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Classification of Elements and Periodicity in Properties · Question 21

JEE Main 2025 (Online) 8th April Evening ShiftMCQEasy📈 Topic in 42% papers+4−1
1

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

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

Answer

(4) 87

Solution

Position of each element in the periodic table:

Z = 32 (Ge): period 4, group 14

Z = 35 (Br): period 4, group 17

Z = 19 (K): period 4, group 1

Z = 87 (Fr): period 7, group 1

Ionisation enthalpy increases across a period, the alkali metals K and Fr have the lowest values in their periods.

Down a group the atomic size increases and the outer electron is farther from the nucleus (more shielding), ionisation enthalpy decreases.

Fr (period 7) has a lower 1st ionisation enthalpy than K (period 4).

The element with the lowest 1st ionisation enthalpy has Z = 87.

Answer: (4)

JEE Main 2025 (Online) 8th April Evening Shift

Keep practising — Classification of Elements and Periodicity in Properties

2

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
3

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
4

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
5

Electronic configuration of four elements A, B, C and D are given below: (A) 1s2 2s2 2p3 (B) 1s2 2s2 2p4 (C) 1s2 2s2 2p5 (D) 1s2 2s2 2p2 Which of the following is the correct order of increasing electronegativity (Pauling's scale)?

  1. D < A < B < C
  2. A < B < C < D
  3. A < C < B < D
  4. A < D < B < C
JEE Main 2025 (Online) 2nd April Evening Shift
6

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

  1. Statement I is incorrect but Statement II is correct
  2. Both Statement I and Statement II are correct
  3. Statement I is correct but Statement II is incorrect
  4. Both Statement I and Statement II are incorrect
JEE Main 2025 (Online) 29th January Morning Shift
7

The incorrect decreasing order of atomic radii is

  1. Si > P > Cl > F
  2. Mg > Al > C > O
  3. Al > B > N > F
  4. Be > Mg > Al > Si
JEE Main 2025 (Online) 28th January Morning Shift
8

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 2025 (Online) 28th January Evening Shift

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