51)
Mg(s) + N₂(g) --> Mg₃N₂(s)
There is one Mg atom on the reactant side and three Mg atoms on the product side. So to balance the number of Mg on both side of the equation a coefficient 3 is placed before Mg on the reactant side. The number of N atoms are two on both side of the reaction. Therefore the balanced chemical equation is,
2Mg(s) + N₂(g) --> Mg₃N₂(s)
52)
The electron configuration of Mg is 1s²2s²2p⁶3s² or [Ne]3s²
The electron configuration of Mg²⁺ is 1s²2s²2p⁶ or [Ne]
The electron configuration of Ne is 1s²2s²2p⁶
Ne he same electron configuration as a Mg²⁺ ion.
53)
Mg has its valence electron in the 3s shell, but Mg²⁺ has no electron in the 3s shell, the valence electron in Mg²⁺is in the 2p orbital. The size of the 2 shell is smaller than the 3 shell. Hence, Mg²⁺ is smaller than Mg.
