A) Be, B, N, C
B) C, N, B, Be
C) Be, N, B, C
D) Be, B, C, N
Correct Answer: A
Solution :
Key Idea Electron affinity is the energy released when an electron is added into a neutral isolated atom in its ground state. Electron affinity generally decreases with increase in atomic size and increases with increase number of electron in outermost shell. In period from left to right EA generally increases because atomic size decreases. So, the order of EA of Be, B, N and C may be as \[N>C>B>Be\] But the EA of nitrogen is much lower due to the presence of half-filled 2p-subshell. So, it is difficult to introduce the electron into stable electronic configuration, (half-filled electronic configuration is more stable) and the EA of II A group (ie. Be) is zero due to completely filled 715-subshell \[(s{{n}^{2}})\]. Therefore, the correct order of electron affinity of Be, B, N and C is as \[\frac{C>N>B>Be}{EA\text{ }decrease}\] or \[\frac{Be<B<N<C}{EA\text{ }increase}\]
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