Question

*10.49 The value of the ionic radius of H in various hydrides varies as shown below. Briefly rationalize these values in terms of the electronegativity of the metal. Compound MgH, LiH NaH KH RH CSH 1.30 1.37 1.46 1.52 1.54 1.52 EN (metal) 2 1. 1 .0 0.9 0.8 0.8 0.7

Answer 1

As we know on moving down the group electronegativity of elements decreases as well as on moving left to right in periodic table it increases . As we can see Magnesium is the first element in group 2 so it have higher electronegativity than other atoms given , so it pulls the electron more efficiently towards itself hence hydride radius is smallest in Magnesium hydride since electron are more towards metal atom than hydrogen atom .

Similarly as the electronegativity decreases the bonding electrons are more towards hydrogen atom than metal atom which causes more repulsion in hydride ion and increases its radii .