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Classification of Elements and Periodicity in Properties

JEE Main 2026 (Online) 28th January Morning ShiftMCQEasy📈 Topic in 19% papers+4−1
Ques. 1JEE Main 2026, 28 January (Morning Shift)

In period 4 of the periodic table, the elements with highest and lowest atomic radii are respectively.

  1. Rb & Br
  2. Na & Cl
  3. K & Br
  4. K & Se

Answer

(3) K & Br

Solution

Period 4 contains the elements from K (Z = 19) to Kr (Z = 36); Rb and Na, Cl are not in period 4, so options (1) and (2) are ruled out.

Across a period the nuclear charge increases while electrons enter the same shell, so the atomic radius decreases from left to right.

Highest atomic radius: K (group 1)

Lowest atomic radius: Br (the last element before the noble gas; the noble gas Kr is not compared, since its radius is a van der Waals radius)

Se lies before Br, so it is larger than Br.

Answer: (3)

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Ques. 2JEE Main 2026, 28 January (Evening Shift)

Consider the elements N, P, O, S, Cl and F. The number of valence electrons present in the elements with most and least metallic character from the above list is respectively.

  1. 7 and 5
  2. 6 and 7
  3. 5 and 7
  4. 5 and 6
Ques. 3JEE Main 2026, 24 January (Morning Shift)

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
Ques. 4JEE Main 2026, 24 January (Evening Shift)

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
Ques. 5JEE Main 2026, 23 January (Morning Shift)

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
Ques. 6JEE Main 2026, 23 January (Evening Shift)

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
Ques. 7JEE Main 2026, 22 January (Morning Shift)

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
Ques. 8JEE Main 2026, 22 January (Evening Shift)

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
Ques. 9JEE Main 2026, 21 January (Morning Shift)

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
Ques. 10JEE Main 2026, 21 January (Evening Shift)

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
Ques. 11JEE Main 2025, 8 April (Evening Shift)

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

  1. 32
  2. 35
  3. 19
  4. 87

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