The value of Zeff for a valence electron in an atom of silicon is?

Zeff is the effective nuclear charge wherein, Z resembles the number of protons in the nucleus while S corresponds to the number of non-valence electrons.

Zeff = Z - S

Silicon has 14 protons; its electron configuration is [Ne] 3s2 3p2. Its non-valence electrons is in the n = 1 and n = 2 shells. There are 2 electrons in n = 1 and 8 in n = 2, so there are a total of 10 non-valence electron.

Z eff = 14-10 = 4

So, the answer is 4.