Question

Would any of the first row transition elements have a specific valence electron quantity, or is that something that varies for each one?

Answer 1

Zn Zinc number 30 always has a valance charge of +2

Explanation:

Zinc has a ground state electron configuration of
`1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10`

When the 3d orbitals are filled as in the case with Zinc the 3d orbitals "fall" down into the third energy level. Being completely filled the 3d sub shell is very stable and the electrons are no longer available for bonding. This leaves only the `4s^2` electrons as valance electrons.

When the Zinc atom loses the 4s electrons it leaves the atom with a +2 charge and a very stable electron configuration
`1s^2 2s^2 2p^6 3s^2 3p^5 3d^10` All the orbitals are completely filled and Zinc is stable.