how do i write the complete electron configuration for Ga3+ and Mg2+????????????

Answer 1

Ga3+
The atomic number of neutral Ga is 31. Atomic number is equal to the number of electrons if the atom is neutral. Since it has a charge of 3+, it means it lost 3 electrons. Therefore, 31 - 3 = 28. Writing the e config: (recall aufbau principle)
Ga : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
Ga 3+ : 1s2 2s2 2p6 3s2 3p6 4s0 3d10
or in Noble Gas core notation,
Ga3+ : [Ar]4s0 3d10

Note that 4s electrons are lost before 3d electrons thus, the electrons are deducted first to the 4s rather than 3d.

Mg2+
Atomic number of Mg is 12. Since the charge is 2+, 2 electrons are lost. Thus, 12 - 2 = 10:
Mg : 1s2 2s2 2p6 3s2
Mg2+ : 1s2 2s2 2p6

Hope this helps~ :)

Answer 2

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