Class 11 : Chemistry (In English) – Chapter 3: Classification of elements and Periodicity in properties

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On June 21, 2025

EXPLANATION & SUMMARY

🔵 Introduction
Chemistry is the science of elements 🧪. By the 18th century, chemists discovered more than 30 elements, and by the 19th century, the number increased rapidly 🌍. As the list grew, arranging them in a logical way became necessary. Imagine learning chemistry if all 118 known elements today were memorized randomly without order ❌. That is why scientists searched for patterns among elements, leading to the development of the Periodic Table — one of the most powerful tools in chemistry.
This chapter focuses on the classification of elements and the periodic properties that recur in predictable patterns.

🟢 Early Attempts of Classification
1️⃣ Dobereiner’s Triads (1829)
Johann Dobereiner grouped elements in sets of three called triads.
The atomic mass of the middle element was roughly the average of the other two.
Example: Li (7), Na (23), K (39).
💡 Limitation: Could not include all elements.
2️⃣ Newlands’ Law of Octaves (1864)
John Newlands arranged elements by increasing atomic mass.
Every 8th element had similar properties, like notes in music 🎶.
Example: Li, Na, K showed similarity.
❌ Limitation: Worked only up to calcium, failed for heavier elements.
3️⃣ Mendeleev’s Periodic Law (1869)
Dmitri Mendeleev arranged elements in increasing atomic mass.
Elements with similar properties were placed in same groups.
Left gaps for undiscovered elements and predicted their properties accurately (e.g., Eka-aluminium → Gallium).
Law: “Properties of elements are periodic function of their atomic masses.”
❌ Limitation: Anomalies in order (Co, Ni), isotopes not explained.

🔵 Modern Periodic Law (1913)
Proposed by Henry Moseley using X-ray spectra.
Law: “Properties of elements are periodic function of their atomic numbers.”
Atomic number (Z = number of protons) became the basis.
Modern Periodic Table is arranged on this principle.

🟢 Structure of the Modern Periodic Table
✔ Arranged in 18 groups (vertical columns) and 7 periods (horizontal rows).
✔ Groups: Elements with similar valence shell electronic configuration.
✔ Periods: Elements with same principal quantum number (n).
✔ Classification:
Group 1 → Alkali metals.
Group 2 → Alkaline earth metals.
Group 17 → Halogens.
Group 18 → Noble gases.
d-block → Transition metals.
f-block → Inner transition elements (lanthanides + actinides).
🌟 Periodicity arises due to repetition of similar valence shell configuration.

🔵 Important Periodic Properties
Now let us explore properties that change periodically across periods and groups.
1️⃣ Atomic Radius (size of atom)
Distance from nucleus to outermost electron.
Across period (→): decreases due to increased nuclear charge pulling electrons closer.
Down group (↓): increases due to addition of shells.
2️⃣ Ionic Radius
Cations (loss of electron) → smaller radius ⚡.
Anions (gain of electron) → larger radius.
3️⃣ Ionization Enthalpy (IE)
Minimum energy to remove an electron.
Across period: increases due to higher nuclear charge.
Down group: decreases because outer electrons are farther, weaker attraction.
Exceptions: Filled/half-filled subshell stability (e.g., O vs N).
4️⃣ Electron Gain Enthalpy (EGE)
Energy change when an electron is added.
Across period: generally becomes more negative (favorable).
Down group: becomes less negative.
Halogens have high negative values. Noble gases ~0.
5️⃣ Electronegativity (EN)
Tendency to attract shared electrons in bond.
Across period: increases.
Down group: decreases.
Fluorine is most electronegative (3.98 Pauling).
6️⃣ Valency
Combining capacity of atom.
Depends on number of valence electrons.
Shows periodicity with group.

🟢 Trends and Anomalies
Diagonal Relationship: Elements of second period show similarities with diagonally placed elements of third period (e.g., Li–Mg, Be–Al).
Inert Pair Effect: Heavier p-block elements show lower oxidation states due to reluctance of s-electrons to participate.
d-block properties: Show variable oxidation states, form colored ions, good catalysts.
f-block elements: Lanthanide contraction influences periodic trends.

🔵 Significance of Periodic Table
✔ Provides systematic arrangement of all known elements.
✔ Predicts chemical and physical properties.
✔ Helps in understanding bonding, reactivity, trends.
✔ Basis of modern chemical research and discovery of new elements.

✨ Conclusion
From Dobereiner’s triads to Moseley’s atomic number law, the periodic table is a triumph of scientific classification 🌍. Periodicity arises from repeating patterns in electronic configuration, which governs properties. This makes the table not just a chart, but a powerful predictive model of matter.

🔹 II. Lesson Summary
📌 Classification of Elements and Periodicity – Key Takeaways
🔵 Early Classification:
Dobereiner’s Triads → average atomic mass rule.
Newlands’ Octaves → repetition every 8th element.
Mendeleev → periodic law of atomic masses, predicted new elements.
🟢 Modern Periodic Law:
Moseley: atomic number as basis.
Periodic properties depend on electronic configuration.
🔴 Structure of Modern Table:
18 groups, 7 periods.
s, p, d, f blocks.
Group trends: alkali metals, halogens, noble gases.
🟡 Periodic Properties:
Atomic radius → decreases across, increases down.
Ionization enthalpy → increases across, decreases down.
Electron gain enthalpy → more negative across, less negative down.
Electronegativity → increases across, decreases down.
Valency → periodic repetition.
🌟 Anomalies:
Diagonal relationships.
Inert pair effect in heavy p-block.
d-block variability, colored ions, catalytic behavior.
Lanthanide contraction.
📚 Importance:
Explains order among elements.
Predicts unknown elements.
Essential tool for chemistry and periodic trends.

📝 Quick Recap:
✔ Classification of elements evolved from triads → octaves → Mendeleev → modern periodic table.
✔ Modern law: properties depend on atomic number, not mass.
✔ Periodic table: 18 groups, 7 periods, 4 blocks (s, p, d, f).
✔ Periodic properties: atomic size, ionization enthalpy, electron gain enthalpy, electronegativity, valency.
✔ Trends explained by nuclear charge and shell structure.
✔ Special features: diagonal relationship, inert pair effect, lanthanide contraction.
✔ Periodic table remains the backbone of chemistry, predicting properties and guiding discovery.

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QUESTIONS FROM TEXTBOOK

🔵 Question 3.1
What is the basic theme of organisation in the periodic table?
🟢 Answer:
✔ The periodic table is based on the Modern Periodic Law:
“The physical and chemical properties of elements are the periodic functions of their atomic numbers.”
✔ Therefore, atomic number (Z) decides an element’s position.
✔ Elements are arranged in increasing Z across periods (rows) and similar-property groups (columns).
➡ This allows prediction of chemical behaviour and trends.

🔵 Question 3.2
Which important property did Mendeleev use to classify the elements in his periodic table and did he stick to that?
🟢 Answer:
✔ He arranged elements by increasing atomic mass.
✔ But, to keep similar properties in one column, he interchanged some (e.g. Co & Ni).
➡ Thus he did not strictly follow mass order—chemical similarity was given priority.

🔵 Question 3.3
What is the basic difference in approach between the Mendeleev’s Periodic Law and the Modern Periodic Law?
🟢 Answer:
Mendeleev Modern
Basis Atomic mass Atomic number
Statement Properties are periodic functions of mass Properties are periodic functions of number
✔ Shift to atomic number removed anomalies like Co–Ni.

🔵 Question 3.4
On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
🟢 Answer:
Electrons fill:
6s → 2 - 4f → 14 - 5d → 10 - 6p → 6
Total = 2 + 14 + 10 + 6 = 32 elements ✅

🔵 Question 3.5
In terms of period and group, where would you locate the element with Z = 114?
🟢 Answer:
Configuration = [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p²
→ Outer 7s² 7p² = Group 14 (p-block)
→ Highest n = 7 = Period 7
➡ Position: Period 7, Group 14, p-block

🔵 Question 3.6
Write the atomic number of the element present in the third period and seventeenth group of the periodic table.
🟢 Answer:
3rd period range = Z 11–18; Group 17 = halogens → Cl (Z = 17) ✅

🔵 Question 3.7
Which element do you think would have been named by
(i) Lawrence Berkeley Laboratory (ii) Seaborg’s group?
🟢 Answer:
(i) Berkelium (Bk) (ii) Seaborgium (Sg) ✅

🔵 Question 3.8
Why do elements in the same group have similar physical and chemical properties?
🟢 Answer:
✔ Same valence-shell configuration ⇒ same valence electrons
➡ Hence similar bonding & chemical behaviour (e.g. Group 1: ns¹).

🔵 Question 3.9
What does atomic radius and ionic radius really mean to you?
🟢 Answer:
Atomic radius: half the distance between nuclei of two identical atoms joined by a covalent bond.
Ionic radius: distance from nucleus to outermost e⁻ in an ion.
💡 Cations < parent atom; Anions > parent atom.

🔵 Question 3.10
How do atomic radii vary in a period and in a group? Explain.
🟢 Answer:
Across a period: ↓ radius (↑ Z → stronger attraction)
Down a group: ↑ radius (new shells added)

🔵 Question 3.11
What do you understand by isoelectronic species? Name one isoelectronic species with each:
(i) F⁻ (ii) Ar (iii) Mg²⁺ (iv) Rb⁺
🟢 Answer:
Isoelectronic = same total electrons.
(i) F⁻ (10 e⁻) → Ne
(ii) Ar (18 e⁻) → K⁺
(iii) Mg²⁺ (10 e⁻) → Na⁺
(iv) Rb⁺ (36 e⁻) → Kr

🔵 Question 3.12
Species: N³⁻, O²⁻, F⁻, Na⁺, Mg²⁺, Al³⁺
(a) Common feature (b) Order of increasing ionic radius
🟢 Answer:
(a) All have 10 e⁻ ⇒ isoelectronic.
(b) Higher Z ⇒ smaller size
Order: Al³⁺ < Mg²⁺ < Na⁺ < F⁻ < O²⁻ < N³⁻

🔵 Question 3.13
Explain why cations are smaller and anions larger than their parent atoms.
🟢 Answer:
Cations: e⁻ lost → repulsion ↓ → effective Z ↑ → radius ↓
Anions: e⁻ gained → repulsion ↑ → effective Z ↓ → radius ↑ ✅

🔵 Question 3.14
What is the significance of the terms “isolated gaseous atom” and “ground state” while defining ionization enthalpy and electron gain enthalpy?
🟢 Answer:
✔ Isolated: Atom not influenced by neighbours → true intrinsic energy.
✔ Gaseous: No intermolecular forces; easy to compare.
✔ Ground state: Lowest-energy configuration; ensures standard reference.
➡ These conditions make the values comparable for all elements.

🔵 Question 3.15
Energy of electron in ground-state H-atom = –2.18 × 10⁻¹⁸ J. Find ionization enthalpy (kJ mol⁻¹).
🟢 Answer:
✳ For 1 atom → 2.18 × 10⁻¹⁸ J
✳ For 1 mol → 2.18 × 10⁻¹⁸ × 6.022 × 10²³ = 1.31 × 10⁶ J mol⁻¹
➡ = 1312 kJ mol⁻¹ ✅

🔵 Question 3.16
Order of actual first ionization enthalpies (kJ mol⁻¹):
Li < B < Be < C < O < N < F < Ne. Explain: (i) Be > B (ii) O < N, F
🟢 Answer:
(i) Be: 2s² (filled) → stable → harder to remove e⁻ → IE ↑
(ii) O: 2p⁴ has paired e⁻ → repulsion → easier removal → IE ↓
✔ Hence given order is correct.

🔵 Question 3.17
Why is IE₁(Na) < IE₁(Mg) but IE₂(Na) ≫ IE₂(Mg)?
🟢 Answer:
Na: 1s²2s²2p⁶3s¹ → removing 3s¹ gives noble-gas core → IE₁ small, IE₂ huge.
Mg: 1s²2s²2p⁶3s² → first e⁻ from 3s², second from 3s¹ → both relatively easy.
➡ Therefore IE₂(Na) ≫ IE₂(Mg). ✅

🔵 Question 3.18
Why does ionization enthalpy decrease down a group?
🟢 Answer:
✔ Atomic size ↑
✔ Shielding ↑
✔ Effective nuclear attraction on valence e⁻ ↓
➡ Easier removal → IE ↓

🔵 Question 3.19
IE₁ (kJ mol⁻¹): B 801, Al 577, Ga 579, In 558, Tl 589. Explain irregularity.
🟢 Answer:
d-/f-electrons in Ga, In, Tl give poor shielding → Z_eff ↑ → IE slightly higher than smooth trend → deviation observed.

🔵 Question 3.20
Which pair has more negative electron gain enthalpy?
(i) O or F (ii) F or Cl
🟢 Answer (corrected):
(i) F < O → F has more negative ΔegH.
(ii) Cl has more negative ΔegH than F (lower repulsion). ✅

🔵 Question 3.21
Second electron-gain enthalpy of O — positive or negative?
🟢 Answer:
Adding e⁻ to O⁻ → O²⁻ faces repulsion → energy absorbed → positive value ✅

🔵 Question 3.22
Difference between electron-gain enthalpy and electronegativity?
🟢 Answer:
Property Electron-gain enthalpy Electronegativity
Definition Energy change on gaining e⁻ Tendency to attract shared e⁻
Type Thermodynamic quantity (kJ mol⁻¹) Relative scale (dimensionless)
Depends on Isolated atom Bonded atom

🔵 Question 3.23
Electronegativity of N is 3.0 in all compounds — true?
🟢 Answer: ❌ False
Electronegativity varies with hybridization, oxidation state, environment; hence not constant.

🔵 Question 3.24
Effect on radius when atom
(a) gains e⁻ (b) loses e⁻
🟢 Answer:
(a) Gain → anion → e–e repulsion ↑ → radius ↑
(b) Loss → cation → Z_eff ↑ → radius ↓ ✅

🔵 Question 3.25
Will isotopes have same first IE?
🟢 Answer:
✔ Same Z and electronic structure → nearly same IE; tiny difference due to mass negligible.

🔵 Question 3.26
Main differences between metals and non-metals:
🟢 Answer:
Metals: lustrous, good conductors, low IE, form cations, basic oxides.
Non-metals: dull, poor conductors, high IE, form anions, acidic oxides.

🔵 Question 3.27
Use periodic table to find:
(a) element with five e⁻ in outer subshell
(b) element tending to lose two e⁻
(c) element tending to gain two e⁻
(d) group containing metal, non-metal, liquid, gas
🟢 Answer (corrected):
(a) F or Cl → outer p⁵
(b) Mg (loses 2 e⁻)
(c) O (gains 2 e⁻)
(d) Group 17:
- Gases F₂, Cl₂ - Liquid Br₂ - Solid I₂ - At shows metallic behaviour ✅

🔵 Question 3.28
Explain why the reactivity order is:
Group 1: Li < Na < K < Rb < Cs Group 17: F > Cl > Br > I
🟢 Answer:
✔ Group 1 (alkali metals) lose one electron to form M⁺.
➡ Down the group:
Atomic size ↑
Ionization enthalpy ↓
→ Electron loss easier → reactivity increases
✅ Order: Li < Na < K < Rb < Cs
✔ Group 17 (halogens) gain one electron to form X⁻.
➡ Down the group:
Size ↑
Electron-gain enthalpy becomes less negative
→ Harder to gain e⁻ → reactivity decreases
✅ Order: F > Cl > Br > I

🔵 Question 3.29
Give the general outer electronic configuration of each block.
🟢 Answer:
s-block: (n)s¹–²
p-block: (n)s² (n)p¹–⁶
d-block: (n–1)d¹–¹⁰ (n)s¹–²
f-block: (n–2)f¹–¹⁴ (n–1)d⁰–¹ (n)s²
Block name depends on where the last electron enters.

🔵 Question 3.30
Assign positions for elements having:
(i) ns²np¹ (ii) (n–1)d¹ns² (n = 4) (iii) (n–2)f⁷(n–1)d¹ns² (n = 6)
🟢 Answer:
(i) ns²np¹ → Group 13, p-block (B family)
(ii) 3d¹4s² → Group 3, Period 4, d-block (Sc)
(iii) 4f⁷5d¹6s² → Group 3, Period 6, f-block (Gd)

🔵 Question 3.31
From the data:
Element ΔH₁ ΔH₂ ΔegH
I 520 7300 –60
II 419 3051 –48
III 1681 3374 –328
IV 1008 1846 –295
V 2372 5251 +48
VI 738 1451 –40
Identify:
(a) least reactive (b) most reactive metal (c) most reactive non-metal
(d) least reactive non-metal (e) metal forming ionic MX (f) metal forming covalent MX
🟢 Answer:
(a) V – high ΔH₁, +ΔegH → inert → least reactive
(b) II – lowest ΔH₁ → most reactive metal
(c) III – very negative ΔegH → most reactive non-metal
(d) V again
(e) II forms stable ionic MX
(f) III forms stable covalent MX

🔵 Question 3.32
Predict formulas of stable binary compounds:
(a) Li & O (b) Mg & N (c) Al & I (d) Si & O (e) P & F (f) Element 71 & F
🟢 Answer:
(a) Li₂O (b) Mg₃N₂ (c) AlI₃ (d) SiO₂ (e) PF₅ (f) LuF₃

🔵 Question 3.33
Period number corresponds to:
(a) atomic number (b) atomic mass (c) principal quantum number (d) azimuthal number
🟢 Answer: (c) ✅

🔵 Question 3.34
Which statement is incorrect?
(a) p-block has 6 columns
(b) d-block has 8 columns
(c) Columns = electrons filling subshell
(d) Block shows value of l
🟢 Answer: (b) ❌ (d-block has 10 columns)

🔵 Question 3.35
Which factor does NOT affect valence shell?
(a) principal quantum number (b) nuclear charge (c) nuclear mass (d) core electrons
🟢 Answer: (c) ✅

🔵 Question 3.36
Size order of F⁻, Ne, Na⁺ depends mainly on:
🟢 Answer: (a) Nuclear charge
All have 10 e⁻; higher Z → smaller radius
➡ Order: Na⁺ < Ne < F⁻ ✅

🔵 Question 3.37
Which statement is incorrect about ionization enthalpy?
(a) Each successive IE is higher
(b) Big rise after valence electrons removed
(c) Large jump marks start of core
(d) Removal from lower n is easier
🟢 Answer: (d) ❌ (Lower-n electrons are harder to remove)

🔵 Question 3.38
Metallic character order for B, Al, Mg, K:
🟢 Answer: K > Mg > Al > B ✅

🔵 Question 3.39
Non-metallic character order for B, C, N, F, Si:
🟢 Answer: F > N > C > B > Si ✅

🔵 Question 3.40
Oxidizing power order for F, Cl, O, N:
🟢 Answer: F > O > Cl > N ✅

NEET QUESTIONS FROM THIS LESSON

🔵 Question 1:
Which one of the following is a d-block element?
🔴 ① Na
🟢 ② Cu
🟡 ③ Al
🔵 ④ Sr
🟢 Answer: ② Cu
📘 Exam: NEET
📅 Year: 2016 | Set: P

🔵 Question 2:
Which element has the highest electronegativity?
🔴 ① F
🟢 ② Cl
🟡 ③ O
🔵 ④ N
🟢 Answer: ① F
📘 Exam: AIPMT
📅 Year: 2012 | Set: C

🔵 Question 3:
Which of the following sets contains only p-block elements?
🔴 ① B, C, N
🟢 ② Na, Mg, Al
🟡 ③ Sc, Ti, V
🔵 ④ K, Ca, Sr
🟢 Answer: ① B, C, N
📘 Exam: NEET
📅 Year: 2018 | Set: R1

🔵 Question 4:
Which group elements are called alkaline earth metals?
🔴 ① Group 1
🟢 ② Group 2
🟡 ③ Group 13
🔵 ④ Group 17
🟢 Answer: ② Group 2
📘 Exam: AIPMT
📅 Year: 2006 | Set: B

🔵 Question 5:
The element with atomic number 35 belongs to:
🔴 ① s-block
🟢 ② p-block
🟡 ③ d-block
🔵 ④ f-block
🟢 Answer: ② p-block
📘 Exam: NEET
📅 Year: 2017 | Set: Q

🔵 Question 6:
The ionization enthalpy is lowest for:
🔴 ① Na
🟢 ② K
🟡 ③ Rb
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: NEET
📅 Year: 2019 | Set: P1

🔵 Question 7:
Which element belongs to Group 17?
🔴 ① F
🟢 ② O
🟡 ③ S
🔵 ④ N
🟢 Answer: ① F
📘 Exam: AIPMT
📅 Year: 2011 | Set: A

🔵 Question 8:
The period number in the long form of periodic table is equal to:
🔴 ① Principal quantum number of valence shell
🟢 ② Azimuthal quantum number of valence shell
🟡 ③ Magnetic quantum number of valence shell
🔵 ④ Spin quantum number of valence electron
🟢 Answer: ① Principal quantum number of valence shell
📘 Exam: NEET
📅 Year: 2020 | Set: S2

🔵 Question 9:
Which one of the following is a metalloid?
🔴 ① Si
🟢 ② Na
🟡 ③ Al
🔵 ④ S
🟢 Answer: ① Si
📘 Exam: AIPMT
📅 Year: 2005 | Set: C

🔵 Question 10:
Which group is known as halogens?
🔴 ① Group 14
🟢 ② Group 15
🟡 ③ Group 16
🔵 ④ Group 17
🟢 Answer: ④ Group 17
📘 Exam: NEET
📅 Year: 2013 | Set: P

🔵 Question 11:
Which element has the highest electron affinity?
🔴 ① F
🟢 ② Cl
🟡 ③ Br
🔵 ④ I
🟢 Answer: ② Cl
📘 Exam: NEET
📅 Year: 2018 | Set: M

🔵 Question 12:
In the modern periodic table, elements are arranged according to:
🔴 ① Atomic mass
🟢 ② Atomic number
🟡 ③ Valency
🔵 ④ Density
🟢 Answer: ② Atomic number
📘 Exam: AIPMT
📅 Year: 2007 | Set: A

🔵 Question 13:
Which period contains the maximum number of elements?
🔴 ① 1st
🟢 ② 2nd
🟡 ③ 6th
🔵 ④ 7th
🟢 Answer: ③ 6th
📘 Exam: NEET
📅 Year: 2015 | Set: L

🔵 Question 14:
The first transition series of the periodic table belongs to:
🔴 ① 3d-series
🟢 ② 4d-series
🟡 ③ 5d-series
🔵 ④ 6d-series
🟢 Answer: ① 3d-series
📘 Exam: NEET
📅 Year: 2014 | Set: O

🔵 Question 15:
The most metallic element among the following is:
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: AIPMT
📅 Year: 2003 | Set: 2

🔵 Question 16:
Which of the following elements is a lanthanoid?
🔴 ① Th
🟢 ② Ce
🟡 ③ U
🔵 ④ Pa
🟢 Answer: ② Ce
📘 Exam: NEET
📅 Year: 2016 | Set: S1

🔵 Question 17:
Which element is a noble gas?
🔴 ① Ne
🟢 ② N
🟡 ③ O
🔵 ④ H
🟢 Answer: ① Ne
📘 Exam: AIPMT
📅 Year: 2009 | Set: A

🔵 Question 18:
Which property generally decreases down a group?
🔴 ① Atomic radius
🟢 ② Metallic character
🟡 ③ Ionization enthalpy
🔵 ④ Electropositivity
🟢 Answer: ③ Ionization enthalpy
📘 Exam: NEET
📅 Year: 2017 | Set: R

🔵 Question 19:
Which group elements are known as alkali metals?
🔴 ① Group 1
🟢 ② Group 2
🟡 ③ Group 13
🔵 ④ Group 14
🟢 Answer: ① Group 1
📘 Exam: NEET
📅 Year: 2019 | Set: O1

🔵 Question 20:
Which of the following pairs are isoelectronic?
🔴 ① Na⁺ and Mg²⁺
🟢 ② K⁺ and Ar
🟡 ③ Ca²⁺ and Cl⁻
🔵 ④ All of these
🟢 Answer: ④ All of these
📘 Exam: AIPMT
📅 Year: 2001 | Set: C

🔵 Question 21:
The correct order of atomic size is:
🔴 ① Na > K > Rb
🟢 ② Rb > K > Na
🟡 ③ K > Na > Rb
🔵 ④ Na > Rb > K
🟢 Answer: ② Rb > K > Na
📘 Exam: NEET
📅 Year: 2020 | Set: P1

🔵 Question 22:
Which one of the following has maximum metallic character?
🔴 ① Na
🟢 ② K
🟡 ③ Rb
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: AIPMT
📅 Year: 2005 | Set: 2

🔵 Question 23:
The valency of an element depends on:
🔴 ① Number of protons
🟢 ② Number of neutrons
🟡 ③ Number of electrons in outermost shell
🔵 ④ Atomic mass
🟢 Answer: ③ Number of electrons in outermost shell
📘 Exam: NEET
📅 Year: 2018 | Set: S

🔵 Question 24:
Which period has only 2 elements?
🔴 ① 1st
🟢 ② 2nd
🟡 ③ 6th
🔵 ④ 7th
🟢 Answer: ① 1st
📘 Exam: AIPMT
📅 Year: 2004 | Set: A

🔵 Question 25:
Which element has the highest ionization energy in the periodic table?
🔴 ① Ne
🟢 ② He
🟡 ③ Ar
🔵 ④ F
🟢 Answer: ② He
📘 Exam: NEET
📅 Year: 2012 | Set: B

🔵 Question 26:
Which one among the following has the lowest ionization enthalpy?
🔴 ① Na
🟢 ② K
🟡 ③ Rb
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: NEET
📅 Year: 2015 | Set: L

🔵 Question 27:
Which of the following elements has the smallest atomic radius?
🔴 ① Li
🟢 ② Be
🟡 ③ B
🔵 ④ C
🟢 Answer: ④ C
📘 Exam: AIPMT
📅 Year: 2010 | Set: A

🔵 Question 28:
The correct order of electron gain enthalpy is:
🔴 ① Cl > F > Br > I
🟢 ② F > Cl > Br > I
🟡 ③ I > Br > Cl > F
🔵 ④ Br > I > F > Cl
🟢 Answer: ① Cl > F > Br > I
📘 Exam: NEET
📅 Year: 2017 | Set: R2

🔵 Question 29:
Which block of elements is characterized by filling of f-orbitals?
🔴 ① s-block
🟢 ② p-block
🟡 ③ d-block
🔵 ④ f-block
🟢 Answer: ④ f-block
📘 Exam: AIPMT
📅 Year: 2002 | Set: B

🔵 Question 30:
Which group element is called oxygen family?
🔴 ① Group 14
🟢 ② Group 15
🟡 ③ Group 16
🔵 ④ Group 17
🟢 Answer: ③ Group 16
📘 Exam: NEET
📅 Year: 2019 | Set: Q1

🔵 Question 31:
Which of the following pairs are not isoelectronic?
🔴 ① CO₂ and N₂O
🟢 ② O₂⁻ and F⁻
🟡 ③ Na⁺ and Mg²⁺
🔵 ④ K⁺ and Ar
🟢 Answer: ① CO₂ and N₂O
📘 Exam: NEET
📅 Year: 2013 | Set: O

🔵 Question 32:
Which one of the following properties increases down the group in the periodic table?
🔴 ① Ionization enthalpy
🟢 ② Electron gain enthalpy
🟡 ③ Metallic character
🔵 ④ Electronegativity
🟢 Answer: ③ Metallic character
📘 Exam: AIPMT
📅 Year: 2005 | Set: C

🔵 Question 33:
Which group is known as noble gases?
🔴 ① 16
🟢 ② 17
🟡 ③ 18
🔵 ④ 15
🟢 Answer: ③ 18
📘 Exam: NEET
📅 Year: 2016 | Set: S1

🔵 Question 34:
Which of the following pairs is not correctly matched?
🔴 ① Alkali metals – Group 1
🟢 ② Alkaline earth metals – Group 2
🟡 ③ Halogens – Group 16
🔵 ④ Noble gases – Group 18
🟢 Answer: ③ Halogens – Group 16
📘 Exam: NEET
📅 Year: 2018 | Set: M

🔵 Question 35:
Which of the following has the largest radius?
🔴 ① F⁻
🟢 ② O²⁻
🟡 ③ Na⁺
🔵 ④ Mg²⁺
🟢 Answer: ② O²⁻
📘 Exam: AIPMT
📅 Year: 2006 | Set: A

🔵 Question 36:
Among alkali metals, the most electropositive element is:
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: NEET
📅 Year: 2014 | Set: Q

🔵 Question 37:
The highest electronegativity value is of:
🔴 ① O
🟢 ② F
🟡 ③ Cl
🔵 ④ N
🟢 Answer: ② F
📘 Exam: AIPMT
📅 Year: 2001 | Set: A

🔵 Question 38:
Which one is not a transition element?
🔴 ① Fe
🟢 ② Cu
🟡 ③ Zn
🔵 ④ Cr
🟢 Answer: ③ Zn
📘 Exam: NEET
📅 Year: 2012 | Set: P

🔵 Question 39:
Which of the following is an actinoid element?
🔴 ① Ce
🟢 ② U
🟡 ③ Yb
🔵 ④ La
🟢 Answer: ② U
📘 Exam: NEET
📅 Year: 2019 | Set: S1

🔵 Question 40:
Which element belongs to Group 15?
🔴 ① N
🟢 ② O
🟡 ③ F
🔵 ④ Ne
🟢 Answer: ① N
📘 Exam: AIPMT
📅 Year: 2007 | Set: B

🔵 Question 41:
Which period contains only two elements?
🔴 ① First
🟢 ② Second
🟡 ③ Sixth
🔵 ④ Seventh
🟢 Answer: ① First
📘 Exam: NEET
📅 Year: 2011 | Set: O

🔵 Question 42:
The correct order of increasing ionization enthalpy is:
🔴 ① Li < Be < B < C
🟢 ② C < B < Be < Li
🟡 ③ Be < Li < C < B
🔵 ④ B < C < Be < Li
🟢 Answer: ① Li < Be < B < C
📘 Exam: NEET
📅 Year: 2017 | Set: P2

🔵 Question 43:
Which of the following has the maximum size?
🔴 ① Na⁺
🟢 ② K⁺
🟡 ③ Rb⁺
🔵 ④ Cs⁺
🟢 Answer: ④ Cs⁺
📘 Exam: AIPMT
📅 Year: 2009 | Set: A

🔵 Question 44:
Which group element is a halogen?
🔴 ① O
🟢 ② Cl
🟡 ③ S
🔵 ④ P
🟢 Answer: ② Cl
📘 Exam: NEET
📅 Year: 2013 | Set: S

🔵 Question 45:
The valency of Mg is:
🔴 ① 1
🟢 ② 2
🟡 ③ 3
🔵 ④ 4
🟢 Answer: ② 2
📘 Exam: AIPMT
📅 Year: 2002 | Set: C

🔵 Question 46:
Which of the following properties increases across a period from left to right?
🔴 ① Metallic character
🟢 ② Ionization enthalpy
🟡 ③ Atomic size
🔵 ④ Electropositivity
🟢 Answer: ② Ionization enthalpy
📘 Exam: NEET
📅 Year: 2018 | Set: O

🔵 Question 47:
Which group elements are known as coinage metals?
🔴 ① Group 10
🟢 ② Group 11
🟡 ③ Group 12
🔵 ④ Group 13
🟢 Answer: ② Group 11
📘 Exam: AIPMT
📅 Year: 2003 | Set: A

🔵 Question 48:
Which of the following is not isoelectronic with Ne?
🔴 ① Na⁺
🟢 ② Mg²⁺
🟡 ③ F⁻
🔵 ④ O²⁻
🟢 Answer: ④ O²⁻
📘 Exam: NEET
📅 Year: 2015 | Set: P

🔵 Question 49:
Which of the following is not a member of halogen family?
🔴 ① F
🟢 ② Cl
🟡 ③ Br
🔵 ④ O
🟢 Answer: ④ O
📘 Exam: AIPMT
📅 Year: 2008 | Set: B

🔵 Question 50:
The correct order of atomic radii is:
🔴 ① F < O < N
🟢 ② N < O < F
🟡 ③ O < F < N
🔵 ④ F < N < O
🟢 Answer: ① F < O < N
📘 Exam: NEET
📅 Year: 2020 | Set: Q1

JEE MAINS QUESTIONS FROM THIS LESSON

🔵 Question 1
The element with Z = 37 belongs to which group in the Modern Periodic Table?
🔴 ① 1
🟢 ② 2
🟡 ③ 17
🔵 ④ 18
🟢 Answer: ① Group 1 (Alkali Metal, Rubidium)
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 2
Which of the following has the highest first ionization enthalpy?
🔴 ① Li
🟢 ② B
🟡 ③ Be
🔵 ④ C
🟢 Answer: ④ C
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 3
Among the following, the correct order of atomic radius is: Na < Mg < Al < Si.
🔴 ① True
🟢 ② False
🟢 Answer: ② False (Correct: Na > Mg > Al > Si)
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 4
Which of the following has the highest electron affinity?
🔴 ① O
🟢 ② F
🟡 ③ Cl
🔵 ④ Br
🟢 Answer: ③ Cl
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 5
Which one of the following oxides is amphoteric?
🔴 ① Na₂O
🟢 ② Al₂O₃
🟡 ③ MgO
🔵 ④ SiO₂
🟢 Answer: ② Al₂O₃
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 6
Which of the following has the largest atomic radius?
🔴 ① K
🟢 ② Na
🟡 ③ Rb
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 7
Which element has the highest electronegativity according to Pauling scale?
🔴 ① Oxygen
🟢 ② Fluorine
🟡 ③ Chlorine
🔵 ④ Nitrogen
🟢 Answer: ② Fluorine
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Evening

🔵 Question 8
Which one among the following has the smallest atomic radius?
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Rb
🟢 Answer: ① Li
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Evening

🔵 Question 9
Which of the following elements shows maximum metallic character?
🔴 ① Na
🟢 ② Mg
🟡 ③ Al
🔵 ④ Si
🟢 Answer: ① Na
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 10
Ionization enthalpy is lowest for:
🔴 ① Li
🟢 ② Cs
🟡 ③ Na
🔵 ④ K
🟢 Answer: ② Cs
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 11
Which of the following elements has the least negative electron gain enthalpy?
🔴 ① O
🟢 ② S
🟡 ③ F
🔵 ④ Cl
🟢 Answer: ① O
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 12
The element with electronic configuration [Ne]3s²3p⁵ is placed in:
🔴 ① Group 16, Period 3
🟢 ② Group 17, Period 3
🟡 ③ Group 17, Period 2
🔵 ④ Group 16, Period 2
🟢 Answer: ② Group 17, Period 3 (Chlorine)
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 13
Which of the following oxides is most acidic?
🔴 ① Na₂O
🟢 ② MgO
🟡 ③ Al₂O₃
🔵 ④ Cl₂O₇
🟢 Answer: ④ Cl₂O₇
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 14
The most electropositive element among the following is:
🔴 ① Na
🟢 ② Mg
🟡 ③ K
🔵 ④ Ca
🟢 Answer: ③ K
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 15
Which of the following noble gases has the highest boiling point?
🔴 ① Ne
🟢 ② Ar
🟡 ③ Kr
🔵 ④ Xe
🟢 Answer: ④ Xe
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 16
Ionization enthalpy decreases in group from top to bottom because:
🔴 ① Atomic size decreases
🟢 ② Atomic size increases
🟡 ③ Nuclear charge increases
🔵 ④ Screening effect decreases
🟢 Answer: ② Atomic size increases
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 17
Which of the following has the most negative electron gain enthalpy?
🔴 ① O
🟢 ② S
🟡 ③ F
🔵 ④ Cl
🟢 Answer: ④ Cl
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 18
Which period of the Modern Periodic Table has maximum number of elements?
🔴 ① 2nd
🟢 ② 4th
🟡 ③ 6th
🔵 ④ 7th
🟢 Answer: ③ 6th period (32 elements)
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Evening

🔵 Question 19
Which among the following has the highest atomic radius?
🔴 ① Mg
🟢 ② Ca
🟡 ③ Sr
🔵 ④ Ba
🟢 Answer: ④ Ba
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 20
The shielding effect is minimum in:
🔴 ① s-orbitals
🟢 ② p-orbitals
🟡 ③ d-orbitals
🔵 ④ f-orbitals
🟢 Answer: ④ f-orbitals
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 21
Which of the following represents diagonal relationship?
🔴 ① Li & Mg
🟢 ② Na & K
🟡 ③ Be & Ba
🔵 ④ B & Al
🟢 Answer: ① Li & Mg
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 22
Which element belongs to d-block?
🔴 ① Na
🟢 ② Fe
🟡 ③ Mg
🔵 ④ Al
🟢 Answer: ② Fe
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Evening

🔵 Question 23
Which of the following noble gases does not form compounds under normal conditions?
🔴 ① Xe
🟢 ② Kr
🟡 ③ Ar
🔵 ④ Ne
🟢 Answer: ④ Ne
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Evening

🔵 Question 24
Which of the following statements is correct?
🔴 ① Atomic radius decreases across a period
🟢 ② Atomic radius increases across a period
🟡 ③ Ionization enthalpy decreases across a period
🔵 ④ Electronegativity decreases across a period
🟢 Answer: ① Atomic radius decreases across a period
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 25
Which one of the following has the highest electronegativity?
🔴 ① Br
🟢 ② Cl
🟡 ③ F
🔵 ④ I
🟢 Answer: ③ F
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 26
Which one of the following pairs of elements belongs to the same group?
🔴 ① Na, Ca
🟢 ② Mg, Ba
🟡 ③ Cl, Br
🔵 ④ O, Cl
🟢 Answer: ③ Cl, Br
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 27
Which of the following elements has the least electronegativity?
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 28
Which of the following pairs is isoelectronic?
🔴 ① Na, Mg
🟢 ② Na⁺, Ne
🟡 ③ K⁺, Ca²⁺
🔵 ④ Cl, Ar
🟢 Answer: ② Na⁺, Ne
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 29
Which period contains the maximum number of elements in the periodic table?
🔴 ① 2nd
🟢 ② 4th
🟡 ③ 6th
🔵 ④ 7th
🟢 Answer: ③ 6th
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 30
Which property increases down the group in the periodic table?
🔴 ① Electronegativity
🟢 ② Metallic character
🟡 ③ Ionization enthalpy
🔵 ④ Non-metallic character
🟢 Answer: ② Metallic character
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Evening

🔵 Question 31
Which is correct order of ionization energy?
🔴 ① Na < Mg < Al < Si
🟢 ② Si < Al < Mg < Na
🟡 ③ Al < Si < Mg < Na
🔵 ④ Mg < Na < Al < Si
🟢 Answer: ① Na < Mg < Al < Si
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Morning

🔵 Question 32
Which element has the electronic configuration [Ne]3s²3p¹?
🔴 ① Na
🟢 ② Mg
🟡 ③ Al
🔵 ④ Si
🟢 Answer: ③ Al
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 33
The electron affinity is highest for:
🔴 ① O
🟢 ② F
🟡 ③ Cl
🔵 ④ Br
🟢 Answer: ③ Cl
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 34
Which one of the following has the largest size?
🔴 ① Na⁺
🟢 ② Mg²⁺
🟡 ③ Al³⁺
🔵 ④ O²⁻
🟢 Answer: ④ O²⁻
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 35
Which of the following shows diagonal relationship?
🔴 ① Be and Al
🟢 ② B and C
🟡 ③ Na and Mg
🔵 ④ Li and K
🟢 Answer: ① Be and Al
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Evening

🔵 Question 36
Which of the following elements belongs to p-block?
🔴 ① Fe
🟢 ② Na
🟡 ③ Cl
🔵 ④ Ca
🟢 Answer: ③ Cl
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Morning

🔵 Question 37
Which among the following has maximum metallic character?
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Rb
🟢 Answer: ④ Rb
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Morning

🔵 Question 38
Which noble gas forms maximum number of compounds?
🔴 ① Ne
🟢 ② Ar
🟡 ③ Kr
🔵 ④ Xe
🟢 Answer: ④ Xe
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 39
Which element of group 17 has the highest electronegativity?
🔴 ① F
🟢 ② Cl
🟡 ③ Br
🔵 ④ I
🟢 Answer: ① F
📘 Exam: JEE Main
📅 Year: 2013 | Shift: Evening

🔵 Question 40
Which of the following has highest effective nuclear charge?
🔴 ① Na
🟢 ② Mg
🟡 ③ Al
🔵 ④ Si
🟢 Answer: ④ Si
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Morning

🔵 Question 41
Which period contains only two elements?
🔴 ① 1st
🟢 ② 2nd
🟡 ③ 3rd
🔵 ④ 4th
🟢 Answer: ① 1st (H & He)
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 42
Which of the following pairs is not isoelectronic?
🔴 ① Na⁺ and Ne
🟢 ② O²⁻ and F⁻
🟡 ③ N³⁻ and Mg²⁺
🔵 ④ Ca²⁺ and Ar
🟢 Answer: ② O²⁻ and F⁻
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Morning

🔵 Question 43
Which element is a metalloid?
🔴 ① Na
🟢 ② Si
🟡 ③ Al
🔵 ④ Ca
🟢 Answer: ② Si
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Evening

🔵 Question 44
Ionization enthalpy is maximum for:
🔴 ① Ne
🟢 ② Ar
🟡 ③ Kr
🔵 ④ Xe
🟢 Answer: ① Ne
📘 Exam: JEE Main
📅 Year: 2015 | Shift: Evening

🔵 Question 45
Which one of the following oxides is neutral?
🔴 ① CO
🟢 ② CO₂
🟡 ③ SO₂
🔵 ④ Na₂O
🟢 Answer: ① CO
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Morning

🔵 Question 46
Which of the following elements has the highest first ionization enthalpy?
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Rb
🟢 Answer: ① Li
📘 Exam: JEE Main
📅 Year: 2019 | Shift: Evening

🔵 Question 47
The most electronegative element is:
🔴 ① F
🟢 ② O
🟡 ③ N
🔵 ④ Cl
🟢 Answer: ① F
📘 Exam: JEE Main
📅 Year: 2017 | Shift: Morning

🔵 Question 48
The general electronic configuration of noble gases is:
🔴 ① ns²np⁵
🟢 ② ns²np⁶
🟡 ③ ns²np⁴
🔵 ④ ns²np³
🟢 Answer: ② ns²np⁶
📘 Exam: JEE Main
📅 Year: 2016 | Shift: Evening

🔵 Question 49
Which of the following has the smallest size?
🔴 ① Na⁺
🟢 ② Mg²⁺
🟡 ③ Al³⁺
🔵 ④ Si⁴⁺
🟢 Answer: ④ Si⁴⁺
📘 Exam: JEE Main
📅 Year: 2018 | Shift: Evening

🔵 Question 50
The element with atomic number 17 belongs to:
🔴 ① Group 16, Period 3
🟢 ② Group 17, Period 3
🟡 ③ Group 16, Period 2
🔵 ④ Group 17, Period 2
🟢 Answer: ② Group 17, Period 3 (Chlorine)
📘 Exam: JEE Main
📅 Year: 2014 | Shift: Evening

JEE ADVANCED QUESTIONS FROM THIS LESSON

🔵 Question 1:
Which one of the following pairs of elements shows diagonal relationship?
🔴 ① Li and Mg
🟢 ② Be and Ba
🟡 ③ Na and K
🔵 ④ B and Al
🟢 Answer: ① Li and Mg
📘 Exam: JEE Advanced
📅 Year: 2010 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 2:
Which element among the following has the highest first ionization enthalpy?
🔴 ① Lithium
🟢 ② Beryllium
🟡 ③ Boron
🔵 ④ Fluorine
🟢 Answer: ④ Fluorine
📘 Exam: JEE Advanced
📅 Year: 2013 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 3:
The element with the lowest electron affinity among the following is:
🔴 ① F
🟢 ② Cl
🟡 ③ O
🔵 ④ Br
🟢 Answer: ③ O
📘 Exam: JEE Advanced
📅 Year: 2016 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 4:
Which one of the following is the correct order of atomic radii?
🔴 ① Na > Mg > Al > Si
🟢 ② Si > Al > Mg > Na
🟡 ③ Na < Mg < Al < Si 🔵 ④ Mg > Na > Al > Si
🟢 Answer: ① Na > Mg > Al > Si
📘 Exam: JEE Advanced
📅 Year: 2017 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 5:
Which one of the following has the maximum metallic character?
🔴 ① Li
🟢 ② Na
🟡 ③ K
🔵 ④ Cs
🟢 Answer: ④ Cs
📘 Exam: JEE Advanced
📅 Year: 2015 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 6:
Which among the following statements is correct about noble gases?
🔴 ① They have maximum electron affinity
🟢 ② They have maximum ionization enthalpy in their respective periods
🟡 ③ They have variable valency
🔵 ④ They are chemically very reactive
🟢 Answer: ② They have maximum ionization enthalpy in their respective periods
📘 Exam: JEE Advanced
📅 Year: 2012 | Paper: 1 | Conducted by: IIT Delhi

🔵 Question 7:
The correct order of electronegativity among the following elements is:
🔴 ① N < O < F
🟢 ② F < O < N
🟡 ③ O < N < F
🔵 ④ N < F < O
🟢 Answer: ① N < O < F
📘 Exam: JEE Advanced
📅 Year: 2011 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 8:
The anomalous properties of the first element of a group are due to:
🔴 ① Large size
🟢 ② Small size, high ionization enthalpy, and high electronegativity
🟡 ③ Low ionization enthalpy
🔵 ④ Presence of d-orbitals
🟢 Answer: ② Small size, high ionization enthalpy, and high electronegativity
📘 Exam: JEE Advanced
📅 Year: 2010 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 9:
Which of the following is not an alkali metal?
🔴 ① Li
🟢 ② K
🟡 ③ Mg
🔵 ④ Na
🟢 Answer: ③ Mg
📘 Exam: JEE Advanced
📅 Year: 2014 | Paper: 1 | Conducted by: IIT Kanpur

🔵 Question 10:
Which one of the following represents the correct trend in ionization enthalpies?
🔴 ① I < Br < Cl < F
🟢 ② F < Cl < Br < I
🟡 ③ Cl < F < Br < I
🔵 ④ Br < I < F < Cl
🟢 Answer: ① I < Br < Cl < F
📘 Exam: JEE Advanced
📅 Year: 2007 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 11:
The electronic configuration of an element is [Ne]3s²3p¹. The element belongs to:
🔴 ① Group 14, Period 3
🟢 ② Group 13, Period 3
🟡 ③ Group 2, Period 3
🔵 ④ Group 15, Period 3
🟢 Answer: ② Group 13, Period 3
📘 Exam: JEE Advanced
📅 Year: 2018 | Paper: 1 | Conducted by: IIT Kanpur

🔵 Question 12:
The element with the highest non-metallic character is:
🔴 ① O
🟢 ② F
🟡 ③ Cl
🔵 ④ N
🟢 Answer: ② F
📘 Exam: JEE Advanced
📅 Year: 2009 | Paper: 1 | Conducted by: IIT Roorkee

🔵 Question 13:
The increasing order of electron affinity among the following is:
🔴 ① F < O < N
🟢 ② N < O < F
🟡 ③ O < N < F
🔵 ④ N < F < O
🟢 Answer: ② N < O < F
📘 Exam: JEE Advanced
📅 Year: 2016 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 14:
Which one of the following represents the correct order of basicity of oxides?
🔴 ① Na₂O > MgO > Al₂O₃ > SiO₂
🟢 ② SiO₂ > Al₂O₃ > MgO > Na₂O
🟡 ③ MgO > Na₂O > Al₂O₃ > SiO₂
🔵 ④ Al₂O₃ > SiO₂ > MgO > Na₂O
🟢 Answer: ① Na₂O > MgO > Al₂O₃ > SiO₂
📘 Exam: JEE Advanced
📅 Year: 2012 | Paper: 1 | Conducted by: IIT Delhi

🔵 Question 15:
Among the following, which has the least metallic character?
🔴 ① Na
🟢 ② K
🟡 ③ Rb
🔵 ④ Li
🟢 Answer: ④ Li
📘 Exam: JEE Advanced
📅 Year: 2017 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 16:
The group number of an element with electronic configuration [Ar]4s²3d¹⁰4p⁵ is:
🔴 ① 16
🟢 ② 17
🟡 ③ 15
🔵 ④ 18
🟢 Answer: ② 17
📘 Exam: JEE Advanced
📅 Year: 2014 | Paper: 1 | Conducted by: IIT Kanpur

🔵 Question 17:
The correct statement is:
🔴 ① Metallic character increases across a period
🟢 ② Metallic character decreases across a period and increases down a group
🟡 ③ Non-metallic character decreases across a period
🔵 ④ Ionization enthalpy decreases across a period
🟢 Answer: ② Metallic character decreases across a period and increases down a group
📘 Exam: JEE Advanced
📅 Year: 2011 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 18:
Which of the following has the highest second ionization enthalpy?
🔴 ① Li
🟢 ② Be
🟡 ③ B
🔵 ④ Na
🟢 Answer: ① Li
📘 Exam: JEE Advanced
📅 Year: 2012 | Paper: 1 | Conducted by: IIT Delhi

🔵 Question 19:
Which of the following elements does not form amphoteric oxide?
🔴 ① Be
🟢 ② Al
🟡 ③ Na
🔵 ④ Zn
🟢 Answer: ③ Na
📘 Exam: JEE Advanced
📅 Year: 2010 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 20:
The most electronegative element among the following is:
🔴 ① O
🟢 ② Cl
🟡 ③ F
🔵 ④ N
🟢 Answer: ③ F
📘 Exam: JEE Advanced
📅 Year: 2014 | Paper: 1 | Conducted by: IIT Kanpur

🔵 Question 21:
Which of the following oxides is acidic?
🔴 ① Na₂O
🟢 ② MgO
🟡 ③ Al₂O₃
🔵 ④ P₂O₅
🟢 Answer: ④ P₂O₅
📘 Exam: JEE Advanced
📅 Year: 2007 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 22:
The correct order of increasing ionic radii is:
🔴 ① F⁻ < O²⁻ < N³⁻
🟢 ② N³⁻ < O²⁻ < F⁻
🟡 ③ O²⁻ < F⁻ < N³⁻
🔵 ④ F⁻ < N³⁻ < O²⁻
🟢 Answer: ② N³⁻ < O²⁻ < F⁻
📘 Exam: JEE Advanced
📅 Year: 2013 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 23:
Which one of the following elements has the least tendency to lose an electron?
🔴 ① Na
🟢 ② K
🟡 ③ F
🔵 ④ Rb
🟢 Answer: ③ F
📘 Exam: JEE Advanced
📅 Year: 2016 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 24:
The order of decreasing atomic radii is:
🔴 ① Na > K > Rb > Cs
🟢 ② Cs > Rb > K > Na
🟡 ③ Rb > Cs > K > Na
🔵 ④ Na > Rb > Cs > K
🟢 Answer: ② Cs > Rb > K > Na
📘 Exam: JEE Advanced
📅 Year: 2009 | Paper: 1 | Conducted by: IIT Roorkee

🔵 Question 25:
The correct order of acidic strength of oxides is:
🔴 ① CO₂ > N₂O₅ > SO₃
🟢 ② N₂O₅ > SO₃ > CO₂
🟡 ③ SO₃ > N₂O₅ > CO₂
🔵 ④ SO₃ > CO₂ > N₂O₅
🟢 Answer: ② N₂O₅ > SO₃ > CO₂
📘 Exam: JEE Advanced
📅 Year: 2018 | Paper: 1 | Conducted by: IIT Kanpur

🔵 Question 26:
Which of the following elements has the smallest atomic radius?
🔴 ① Be
🟢 ② B
🟡 ③ C
🔵 ④ N
🟢 Answer: ④ N
📘 Exam: JEE Advanced
📅 Year: 2011 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 27:
The maximum value of electronegativity is assigned to:
🔴 ① O
🟢 ② N
🟡 ③ Cl
🔵 ④ F
🟢 Answer: ④ F
📘 Exam: JEE Advanced
📅 Year: 2015 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 28:
Which of the following properties increases down the group in the periodic table?
🔴 ① Ionization enthalpy
🟢 ② Metallic character
🟡 ③ Electronegativity
🔵 ④ Non-metallic character
🟢 Answer: ② Metallic character
📘 Exam: JEE Advanced
📅 Year: 2010 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 29:
The least metallic element among the following is:
🔴 ① Na
🟢 ② Mg
🟡 ③ Al
🔵 ④ Si
🟢 Answer: ④ Si
📘 Exam: JEE Advanced
📅 Year: 2017 | Paper: 1 | Conducted by: IIT Madras

🔵 Question 30:
The anomalous behaviour of lithium is due to:
🔴 ① Large atomic size
🟢 ② Small atomic size and high charge density
🟡 ③ Low ionization energy
🔵 ④ Presence of d-orbitals
🟢 Answer: ② Small atomic size and high charge density
📘 Exam: JEE Advanced
📅 Year: 2012 | Paper: 1 | Conducted by: IIT Delhi

🔵 Question 31:
The correct order of stability of hydrides is:
🔴 ① CH₄ > NH₃ > H₂O > HF
🟢 ② HF > H₂O > NH₃ > CH₄
🟡 ③ NH₃ > HF > CH₄ > H₂O
🔵 ④ H₂O > NH₃ > CH₄ > HF
🟢 Answer: ② HF > H₂O > NH₃ > CH₄
📘 Exam: JEE Advanced
📅 Year: 2008 | Paper: 1 | Conducted by: IIT Roorkee

🔵 Question 32:
Among the following, which has the maximum electron affinity?
🔴 ① Cl
🟢 ② F
🟡 ③ Br
🔵 ④ I
🟢 Answer: ① Cl
📘 Exam: JEE Advanced
📅 Year: 2013 | Paper: 1 | Conducted by: IIT Bombay

🔵 Question 33:
Which of the following does not belong to the s-block of periodic table?
🔴 ① Li
🟢 ② Be
🟡 ③ Al
🔵 ④ Ca
🟢 Answer: ③ Al
📘 Exam: JEE Advanced
📅 Year: 2016 | Paper: 1 | Conducted by: IIT Guwahati

🔵 Question 34:
The element with configuration [Kr]5s²4d¹⁰5p⁶ belongs to:
🔴 ① Group 17
🟢 ② Group 18
🟡 ③ Group 16
🔵 ④ Group 2
🟢 Answer: ② Group 18
📘 Exam: JEE Advanced
📅 Year: 2018 | Paper: 1 | Conducted by: IIT Kanpur

PRACTICE SETS FROM THIS LESSON

🔵 Question 1:
The modern periodic table is based on:
🔴 ① Atomic mass
🟢 ② Atomic number
🟡 ③ Neutron number
🔵 ④ Isotopic mass
🟢 Answer: ② Atomic number
🎯 Difficulty: NEET

🔵 Question 2:
Who is credited with the discovery of the periodic law based on atomic numbers?
🔴 ① Mendeleev
🟢 ② Moseley
🟡 ③ Newlands
🔵 ④ Dobereiner
🟢 Answer: ② Moseley
🎯 Difficulty: NEET

🔵 Question 3:
Which group of elements is known as alkaline earth metals?
🔴 ① Group 1
🟢 ② Group 2
🟡 ③ Group 16
🔵 ④ Group 17
🟢 Answer: ② Group 2
🎯 Difficulty: NEET

🔵 Question 4:
Which group elements are also called halogens?
🔴 ① Group 15
🟢 ② Group 16
🟡 ③ Group 17
🔵 ④ Group 18
🟢 Answer: ③ Group 17
🎯 Difficulty: NEET

🔵 Question 5:
The elements with atomic numbers 3, 11, 19 belong to:
🔴 ① s-block
🟢 ② p-block
🟡 ③ d-block
🔵 ④ f-block
🟢 Answer: ① s-block
🎯 Difficulty: NEET

🔵 Question 6:
The d-block elements are also called:
🔴 ① Alkali metals
🟢 ② Transition elements
🟡 ③ Inner transition elements
🔵 ④ Noble gases
🟢 Answer: ② Transition elements
🎯 Difficulty: NEET

🔵 Question 7:
The element with atomic number 18 belongs to which group?
🔴 ① Group 16
🟢 ② Group 17
🟡 ③ Group 18
🔵 ④ Group 2
🟢 Answer: ③ Group 18
🎯 Difficulty: NEET

🔵 Question 8:
Lanthanides belong to which block of the periodic table?
🔴 ① s-block
🟢 ② p-block
🟡 ③ d-block
🔵 ④ f-block
🟢 Answer: ④ f-block
🎯 Difficulty: NEET

🔵 Question 9:
Which property generally increases across a period from left to right?
🔴 ① Atomic radius
🟢 ② Ionization enthalpy
🟡 ③ Metallic character
🔵 ④ Electropositive nature
🟢 Answer: ② Ionization enthalpy
🎯 Difficulty: NEET

🔵 Question 10:
Which property decreases down a group in the periodic table?
🔴 ① Atomic radius
🟢 ② Metallic character
🟡 ③ Ionization enthalpy
🔵 ④ Density
🟢 Answer: ③ Ionization enthalpy
🎯 Difficulty: NEET

🔵 Question 11:
Which of the following elements has the highest electronegativity?
🔴 ① Chlorine
🟢 ② Fluorine
🟡 ③ Oxygen
🔵 ④ Nitrogen
🟢 Answer: ② Fluorine
🎯 Difficulty: NEET

🔵 Question 12:
The general electronic configuration of alkali metals is:
🔴 ① ns²
🟢 ② ns¹
🟡 ③ ns²np⁶
🔵 ④ ns²np⁵
🟢 Answer: ② ns¹
🎯 Difficulty: NEET

🔵 Question 13:
Which element has the smallest atomic radius in period 2?
🔴 ① Li
🟢 ② Be
🟡 ③ F
🔵 ④ Ne
🟢 Answer: ④ Ne
🎯 Difficulty: NEET

🔵 Question 14:
Which of the following elements is a metalloid?
🔴 ① Na
🟢 ② Si
🟡 ③ Mg
🔵 ④ Cl
🟢 Answer: ② Si
🎯 Difficulty: NEET

🔵 Question 15:
Which property shows periodicity due to the periodic variation in effective nuclear charge?
🔴 ① Atomic volume
🟢 ② Ionization enthalpy
🟡 ③ Colour
🔵 ④ Density
🟢 Answer: ② Ionization enthalpy
🎯 Difficulty: NEET

🔵 Question 16:
The tendency to gain electrons is called:
🔴 ① Ionization energy
🟢 ② Electron gain enthalpy
🟡 ③ Electronegativity
🔵 ④ Reducing power
🟢 Answer: ② Electron gain enthalpy
🎯 Difficulty: NEET

🔵 Question 17:
Which noble gas has the lowest boiling point?
🔴 ① He
🟢 ② Ne
🟡 ③ Ar
🔵 ④ Kr
🟢 Answer: ① He
🎯 Difficulty: NEET

🔵 Question 18:
The shielding effect is minimum for:
🔴 ① s-electrons
🟢 ② p-electrons
🟡 ③ d-electrons
🔵 ④ f-electrons
🟢 Answer: ① s-electrons
🎯 Difficulty: NEET

🔵 Question 19:
Which element has the highest metallic character in period 3?
🔴 ① Na
🟢 ② Al
🟡 ③ Si
🔵 ④ Cl
🟢 Answer: ① Na
🎯 Difficulty: NEET

🔵 Question 20:
The element with the highest first ionization enthalpy is:
🔴 ① F
🟢 ② Ne
🟡 ③ He
🔵 ④ Ar
🟢 Answer: ③ He
🎯 Difficulty: NEET

🔵 Question 21:
The element with the lowest electron gain enthalpy is:
🔴 ① F
🟢 ② Ne
🟡 ③ Ar
🔵 ④ Cl
🟢 Answer: ② Ne
🎯 Difficulty: NEET

🔵 Question 22:
Which group element shows inert pair effect prominently?
🔴 ① Group 13
🟢 ② Group 14
🟡 ③ Group 15
🔵 ④ Group 16
🟢 Answer: ② Group 14
🎯 Difficulty: NEET

🔵 Question 23:
The most electropositive element is:
🔴 ① Na
🟢 ② Cs
🟡 ③ Mg
🔵 ④ Li
🟢 Answer: ② Cs
🎯 Difficulty: NEET

🔵 Question 24:
Across a period, the basic character of oxides:
🔴 ① Increases
🟢 ② Decreases
🟡 ③ Remains constant
🔵 ④ First increases, then decreases
🟢 Answer: ② Decreases
🎯 Difficulty: NEET

🔵 Question 25:
The atomic radius of Li, Na, K increases in the order because:
🔴 ① Nuclear charge decreases
🟢 ② Number of shells increases
🟡 ③ Shielding decreases
🔵 ④ Effective nuclear charge increases
🟢 Answer: ② Number of shells increases
🎯 Difficulty: NEET

🔵 Question 26:
Which one of the following oxides is amphoteric?
🔴 ① Na₂O
🟢 ② Al₂O₃
🟡 ③ MgO
🔵 ④ P₂O₅
🟢 Answer: ② Al₂O₃
🎯 Difficulty: JEE Main

🔵 Question 27:
Which of the following sets of elements belong to the same group?
🔴 ① Na, Mg, K
🟢 ② Li, Na, K
🟡 ③ B, C, N
🔵 ④ O, F, Ne
🟢 Answer: ② Li, Na, K
🎯 Difficulty: JEE Main

🔵 Question 28:
The highest electron affinity among halogens is observed for:
🔴 ① I
🟢 ② Br
🟡 ③ Cl
🔵 ④ F
🟢 Answer: ③ Cl
🎯 Difficulty: JEE Main

🔵 Question 29:
Which of the following elements has the maximum shielding effect?
🔴 ① 1s electron
🟢 ② 2p electron
🟡 ③ 3d electron
🔵 ④ 4f electron
🟢 Answer: ④ 4f electron
🎯 Difficulty: JEE Main

🔵 Question 30:
Which among the following has the largest atomic radius?
🔴 ① Li
🟢 ② K
🟡 ③ Na
🔵 ④ Rb
🟢 Answer: ④ Rb
🎯 Difficulty: JEE Main

🔵 Question 31:
Among the following, which has the least ionization enthalpy?
🔴 ① Na
🟢 ② K
🟡 ③ Rb
🔵 ④ Cs
🟢 Answer: ④ Cs
🎯 Difficulty: JEE Main

🔵 Question 32:
Which element shows maximum non-metallic character in period 3?
🔴 ① Cl
🟢 ② S
🟡 ③ P
🔵 ④ Si
🟢 Answer: ① Cl
🎯 Difficulty: JEE Main

🔵 Question 33:
In which group of the periodic table do elements exhibit variable valency most frequently?
🔴 ① s-block
🟢 ② p-block
🟡 ③ d-block
🔵 ④ f-block
🟢 Answer: ③ d-block
🎯 Difficulty: JEE Main

🔵 Question 34:
Which one of the following pairs of elements is a Dobereiner triad?
🔴 ① Li, Na, K
🟢 ② Cl, Br, I
🟡 ③ Ca, Sr, Ba
🔵 ④ All of these
🟢 Answer: ④ All of these
🎯 Difficulty: JEE Main

🔵 Question 35:
Ionization enthalpy generally decreases down the group due to:
🔴 ① Increase in nuclear charge
🟢 ② Increase in atomic size
🟡 ③ Decrease in shielding effect
🔵 ④ Increase in effective nuclear charge
🟢 Answer: ② Increase in atomic size
🎯 Difficulty: JEE Main

🔵 Question 36:
Which of the following statements is correct regarding electronegativity?
🔴 ① It increases down a group.
🟢 ② It decreases across a period.
🟡 ③ It increases across a period.
🔵 ④ It remains constant across a period.
🟢 Answer: ③ It increases across a period.
🎯 Difficulty: JEE Main

🔵 Question 37:
Which one among the following elements has the maximum density?
🔴 ① Li
🟢 ② K
🟡 ③ Cs
🔵 ④ Na
🟢 Answer: ③ Cs
🎯 Difficulty: JEE Main

🔵 Question 38:
Which one of the following pairs has the same number of valence electrons?
🔴 ① O, S
🟢 ② N, F
🟡 ③ C, Na
🔵 ④ H, Li
🟢 Answer: ① O, S
🎯 Difficulty: JEE Main

🔵 Question 39:
Which of the following belongs to the p-block of periodic table?
🔴 ① Calcium
🟢 ② Sulphur
🟡 ③ Sodium
🔵 ④ Iron
🟢 Answer: ② Sulphur
🎯 Difficulty: JEE Main

🔵 Question 40:
The maximum number of elements in 5th period of periodic table is:
🔴 ① 8
🟢 ② 18
🟡 ③ 32
🔵 ④ 50
🟢 Answer: ② 18
🎯 Difficulty: JEE Main

🚀 Advanced-level (Q41–Q50):

🔵 Question 41:
Which pair of successive ionization enthalpies shows the largest jump for magnesium?
🔴 ① IE₁ and IE₂
🟢 ② IE₂ and IE₃
🟡 ③ IE₃ and IE₄
🔵 ④ IE₄ and IE₅
🟢 Answer: ② IE₂ and IE₃
🎯 Difficulty: JEE Advanced

🔵 Question 42:
If the first ionization enthalpy of Na is 496 kJ/mol and that of Mg is 738 kJ/mol, the higher value for Mg is due to:
🔴 ① Greater atomic size of Mg
🟢 ② Greater effective nuclear charge of Mg
🟡 ③ Smaller nuclear charge of Na
🔵 ④ Strong shielding effect in Na
🟢 Answer: ② Greater effective nuclear charge of Mg
🎯 Difficulty: JEE Advanced

🔵 Question 43:
Which of the following trends is NOT correctly represented?
🔴 ① Metallic character ↓ down a group
🟢 ② Atomic radius ↑ down a group
🟡 ③ Electronegativity ↑ down a group
🔵 ④ Ionization enthalpy ↓ down a group
🟢 Answer: ③ Electronegativity ↑ down a group
🎯 Difficulty: JEE Advanced

🔵 Question 44:
Which of the following pairs of elements are diagonal relatives?
🔴 ① Li and Mg
🟢 ② Be and Al
🟡 ③ B and Si
🔵 ④ All of these
🟢 Answer: ④ All of these
🎯 Difficulty: JEE Advanced

🔵 Question 45:
The first ionization enthalpies of B and Be are 801 kJ/mol and 900 kJ/mol respectively. This is because:
🔴 ① Be has smaller size than B
🟢 ② Be has completely filled 2s orbital
🟡 ③ B has greater effective nuclear charge
🔵 ④ B has half-filled stability
🟢 Answer: ② Be has completely filled 2s orbital
🎯 Difficulty: JEE Advanced

🔵 Question 46:
Which of the following elements has the least metallic character?
🔴 ① Na
🟢 ② Al
🟡 ③ Cl
🔵 ④ Mg
🟢 Answer: ③ Cl
🎯 Difficulty: JEE Advanced

🔵 Question 47:
Across a period, electron affinity initially increases but fluorine has slightly lower electron affinity than chlorine due to:
🔴 ① Smaller size of chlorine
🟢 ② High electron-electron repulsion in fluorine
🟡 ③ Stronger nuclear attraction in fluorine
🔵 ④ Low electronegativity of chlorine
🟢 Answer: ② High electron-electron repulsion in fluorine
🎯 Difficulty: JEE Advanced

🔵 Question 48:
Which of the following has the highest second ionization enthalpy?
🔴 ① Na
🟢 ② Mg
🟡 ③ Al
🔵 ④ Si
🟢 Answer: ① Na
🎯 Difficulty: JEE Advanced

🔵 Question 49:
Which statement about effective nuclear charge (Zeff) is correct?
🔴 ① Zeff decreases across a period
🟢 ② Zeff increases across a period
🟡 ③ Zeff remains constant across a period
🔵 ④ Zeff decreases with increase in atomic number
🟢 Answer: ② Zeff increases across a period
🎯 Difficulty: JEE Advanced

🔵 Question 50:
Which of the following elements has the maximum non-metallic character?
🔴 ① O
🟢 ② F
🟡 ③ N
🔵 ④ Cl
🟢 Answer: ② F
🎯 Difficulty: JEE Advanced

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