Question #b193a

1 Answer
Nov 17, 2017

It has a full 3d shell and starts filling the 4p shell.

Explanation:

The 4p shell is farther from the nucleus than the 3d shell (4th energy level) and also the filling of the 4p shell in Ga means there is only 1 valence electron in Ga as opposed to the 10 valence electrons in Zn. This means the effective nuclear charge in Ga is only 1 compared to the effective nuclear charge of 20 in Zn. The smaller the effective nuclear charge, the larger the atom.