Question

Give reasons: 

(i) Coordination number of Be is 4, but that of Mg is six 

(ii) Lithium iodide is covalent but potassium iodide is ionic.

Answer 1

(i) Beryllium does not have ‘d’ subshell in n = 2 level. It has only 4 valence orbital. 

Hence it can have a coordination number 4. 

Mg has ‘d’ subshells in n = 3 level. Hence it has more valence orbital. Therefore it can have a coordination number 6. 

(ii) Lithium iodide is covalent because of the smaller atomic size of lithium atom, it distorts to the electron to the electron cloud of iodine towards it. Or K has less polarizing power than Li⁺.