Why does Ga have one unpaired electron?

Such as for example P has three unpaired electrons (because of its electron configuration) but I don't understand why Ga has one unpaired electron - wouldn't it be five (electron configuration)?

Thank you!

1 answer

Look at 30Zn. That is 1s2 2s2 2p6 3s2 3p6 3d10 4s2.Add 1 more as a 4p1 and that's it.
OR, look at it as As minus 3 electrons. If P and As have 3 unpaired, then take two away and Ga has 3-2 = 1.