Based on their valence-shell electron configurations which of the following species would you expect to have the greatest electron affinity : (a)Be_2; (b)F_2; (c) (B_2)+; (d) (C_2)+

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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(a) Be2 :

Beryllium has an atomic number of 4. 

Electronic configuration: 1s2, 2s2.

Be2 is a gas and its orbitals are fully occupied and hence will have very low/nil electron affinity. 

(b) F2: 

Fluorine has an atomic number of 9.

Electronic configuration: 1s2, 2s2, 2p5

Here two atoms of fluorine have bonded together and will have low electron affinity (vacancy of 2 electrons in 2 atoms).

(c) (B_2)+

Atomic number of boron = 5

electronic configuration: 1s2, 2s2, 2p1.

and here the boron atoms have lost the p-orbital electron, and so have less affinity for electrons.

(d) (C_2)+

Carbon has an atomic number of 6

electronic configuration: 1s2, 2s2, 2p2

In the given scenario, (d) will have the highest affinity for electrons, since its p-orbital is mostly unfilled.