chemistry peridic classification

Question

Arrange the following species in the increasing order of ionic radii. N 3- , F- , Na+ , Mg2+, O2- and Al3+. (c) H2O(g)  H(g) +OH (g) ; ∆aH°1= 502 kJmol-1 OH(g) H(g)+ O(g) ; ∆aH°2= 427kJmol-1 Why is ∆aH°1 and ∆aH°2 different for water?

Answer 1

All these ions have 10 electrons in their shell therefore these are isoelectronic speicies
The more + the charge, the smaller the ionic radius. Remember that - means adding electrons. These electrons go in the outermost shells. Also, when an atom loses electrons, it clings ever more tightly to the ones it has left, further reducing the ionic radius. therefore the order of ionic radii will be:

Al³⁺ < Mg²⁺ < Na⁺ < F⁻ < O²⁻ < N³⁻ (increasing order)