among oxygen O^2- ion and magnesium Mg²⁺ ion what has larger sizes and why???????????????

Among oxygen O^2- ion and magnesium Mg²⁺ ion, O^2- ion is larger than Mg²⁺.

Magnesium, Mg, forms the magnesium ion Mg^2+, by losing two electrons. The electronic structure changes from 2,8,2 in Mg to 2,8 in Mg²⁺ , so Mg²⁺ ion is smaller than its atom. While oxygen forms the oxide ion by gaining two electrons. The electronic structure changes from 2, 6 in the O atom to 2,8 in the O^2- ion, so it is larger in size than its atom.

Between these two ions, O^2- ion is larger than Mg²⁺ ion, because cations are formed by the loose of electrons and due to this the nuclear charge on electron in subshell increases & the size decreases due to more attraction. when atom gains electron then the nuclear charge decreases & size increases. so size of cation is less than anions. And size of O^2- ion is larger than Mg²⁺.