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Classification of Elements and Periodicity in Properties · Question 14

JEE Main 2026 (Online) 24th January Evening ShiftMCQMedium📈 Topic in 42% papers+4−1
1

The correct order of C, N, O and F in terms of second ionisation potential is

  1. C < N < F < O
  2. C < F < N < O
  3. F < N < C < O
  4. C < O < N < F

Answer

(1) C < N < F < O

Solution

Second ionisation removes an electron from the unipositive ion:

C+: 2s2 2p1; N+: 2s2 2p2; O+: 2s2 2p3; F+: 2s2 2p4

Across the period IE2 rises with nuclear charge, but O+ has a stable half-filled 2p3 configuration, so removing an electron from it is harder than from F+ (2p4).

IE2 ( kJ mol-1): C 2353, N 2856, O 3388, F 3374

C < N < F < O

Answer: (1)

JEE Main 2026 (Online) 24th January Evening Shift

Keep practising — Classification of Elements and Periodicity in Properties

2

The correct trend in the first ionization enthalpies of the elements in the 3rd period of periodic table is :

  1. Si < S < Al < P < Cl
  2. Al < Si < S < P < Cl
  3. S < Si < Al < P < Cl
  4. Al < S < P < Si < Cl
JEE Main 2026 (Online) 23rd January Morning Shift
3

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is true but Statement II is false
  2. Statement I is false but Statement II is true
  3. Both Statement I and Statement II are true
  4. Both Statement I and Statement II are false
JEE Main 2026 (Online) 23rd January Evening Shift
4

A 'p'-block element (E) and hydrogen form a binary cation (EHx)+, while EH3 on treatment with K2HgI4 in alkaline medium gives a precipitate of basic mercury(II) amido-iodine. Given below are first ionisation enthalpy values ( kJ mol-1) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.

  1. 1402
  2. 1086
  3. 801
  4. 1312
JEE Main 2026 (Online) 22nd January Morning Shift
5

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are false
  2. Statement I is false but Statement II is true
  3. Statement I is true but Statement II is false
  4. Both Statement I and Statement II are true
JEE Main 2026 (Online) 22nd January Evening Shift
6

Which of the following represents the correct trend for the mentioned property? Choose the correct answer from the options given below :

  1. B and C only
  2. A, B and D only
  3. A and B only
  4. A, B, C and D
JEE Main 2026 (Online) 21st January Morning Shift
7

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is true but Statement II is false
  2. Both Statement I and Statement II are true
  3. Statement I is false but Statement II is true
  4. Both Statement I and Statement II are false
JEE Main 2026 (Online) 21st January Evening Shift
8

The atomic number of the element from the following with lowest 1st ionisation enthalpy is :

  1. 32
  2. 35
  3. 19
  4. 87
JEE Main 2025 (Online) 8th April Evening Shift
9

Choose the incorrect trend in the atomic radii (r) of the elements.

  1. rRb < rCs
  2. rAt < rCs
  3. rBr < rK
  4. rMg < rAl
JEE Main 2025 (Online) 7th April Evening Shift
10

Which of the following statements are correct? Choose the correct answer from the options given below:

  1. A, C and D Only
  2. B and C Only
  3. B and D Only
  4. B, C and E Only
JEE Main 2025 (Online) 3rd April Morning Shift
11

Match the LIST-I with LIST-II Choose the correct answer from the options given below:

  1. A-IV, B-I, C-II, D-III
  2. A-IV, B-III, C-I, D-II
  3. A-III, B-I, C-IV, D-II
  4. A-II, B-III, C-IV, D-I
JEE Main 2025 (Online) 3rd April Evening Shift

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