Chapter Exam

Unit 9: Classification of Elements and Periodicity in Properties — Online MCQ Test

Q: Which of the following electronegativity order is incorrect?

Answer: D. N > C > B — Electronegativity increases across a period. The correct order for Period 3 is Cl > S > P. Thus, P > S > Cl is incorrect.

Q: Match List-I with List-II: (A) Al3+ < Mg2+ < Na+ < F- (I) Ionisation Enthalpy (B) B < C < O < N (II) Metallic character (C) B < Al < Mg < K (III) Electronegativity (D) Si < P < S < Cl (IV) Ionic radii

Answer: A. (A)-(IV), (B)-(I), (C)-(II), (D)-(III) — Matching based on atomic properties: (A) is ionic radii order, (B) ionisation enthalpy (N is higher than O due to stable half-filled), (C) metallic character increases down and left, (D) electronegativity increases across period.

Q: The correct order of metallic character is =

Answer: A. K > Ca > Be — Metallic character increases down a group and decreases across a period. Potassium, an alkali metal, is more metallic than calcium, and calcium is more metallic than beryllium because Be is much higher in the group and smaller in size. Thus the order is $\mathrm{K > Ca > Be}$.

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Unit 9: Classification of Elements and Periodicity in Properties — Important Questions & Answers (FAQ)

Frequently asked questions from JEE JEE MAINS CHEMISTRY — Unit 9: Classification of Elements and Periodicity in Properties, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following electronegativity order is incorrect?

A. F > O > N
B. C > B > Be
C. P > S > Cl
D. N > C > B ✓

Answer: D. N > C > B
Electronegativity increases across a period. The correct order for Period 3 is Cl > S > P. Thus, P > S > Cl is incorrect.

Which of the following electronegativity order is incorrect?

A. Mg < Be < B < N
B. S < Cl < O < F
C. Al < Si < C < N
D. Al < Mg < B < N ✓

Answer: D. Al < Mg < B < N
Electronegativity generally increases across a period and decreases down a group. In option (4), Al < Mg is incorrect because Mg (group 2) is to the left of Al (group 13) in the same period; typically, electronegativity increases from left to right (Mg > Al).

Match List-I with List-II: (A) Al3+ < Mg2+ < Na+ < F- (I) Ionisation Enthalpy (B) B < C < O < N (II) Metallic character (C) B < Al < Mg < K (III) Electronegativity (D) Si < P < S < Cl (IV) Ionic radii

A. (A)-(IV), (B)-(I), (C)-(II), (D)-(III) ✓
B. (A)-(IV), (B)-(I), (C)-(III), (D)-(II)
C. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
D. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)

Answer: A. (A)-(IV), (B)-(I), (C)-(II), (D)-(III)
Matching based on atomic properties: (A) is ionic radii order, (B) ionisation enthalpy (N is higher than O due to stable half-filled), (C) metallic character increases down and left, (D) electronegativity increases across period.

Given below are two statements: Statement-I: The correct order in terms of atomic/ionic radii is Al > Mg > Mg2+ > Al3+. Statement-II: The correct order in terms of the magnitude of electron gain enthalpy is Cl > Br > S > O. In the light of the above statements, choose the correct answer:

A. (1) Both Statement I and Statement II are false
B. (2) Statement I is false but Statement II is true ✓
C. (3) Statement I is true but Statement II is false
D. (4) Both Statement I and Statement II are true

Answer: B. (2) Statement I is false but Statement II is true
Correct order for atomic/ionic radii is Mg > Al > Mg2+ > Al3+. Statement I is false. Statement II is true as Chlorine has the highest electron gain enthalpy.

The correct order of metallic character is =

A. K > Ca > Be ✓
B. Be > Ca > K
C. K > Be > Ca
D. Ca > K > Be

Answer: A. K > Ca > Be
Metallic character increases down a group and decreases across a period. Potassium, an alkali metal, is more metallic than calcium, and calcium is more metallic than beryllium because Be is much higher in the group and smaller in size. Thus the order is $\mathrm{K > Ca > Be}$.

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