Option A: 3
The atomic number of gallium atom is 31. It belongs to 13th group and 4th period of the periodic table.
The electronic configuration is as follows:
[tex] [Ar]3d^{10}4s^{2}4p^{1} [/tex]
Here, Ar is the nearest noble gas.
The outermost electronic shells are [tex] 4s^{2}4p^{1}. [/tex]
From the electronic configuration, valence electrons of gallium are 3.
