sblock Elements 2 Question 1
1. In comparison to boron, berylium has (2019 Main, 12 April II)
(a) lesser nuclear charge and lesser first ionisation enthalpy
(b) greater nuclear charge and lesser first ionisation enthalpy
(c) greater nuclear charge and greater first ionisation enthalpy
(d) lesser nuclear charge and greater first ionisation enthalpy
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Answer:
Correct Answer: 1. (d)
Solution:
- In comparison to boron, beryllium has lesser nuclear charge and greater first ionisation enthalpy.
Electronic configuration of $\operatorname{Be}(4)=1 s^{2}, 2 s^{2}$.
It possess completely filled $s$-orbitals. Hence, high amount of energy is required to pull the electron from the gaseous atom. Beryllium (4) lies left to the boron (5) and on moving from left to right an electron is added due to which nuclear charge increases from Be to B.
