Question

Variation of first ionization enthalpies with Z = 1 to 60.

Study the figure given above and answer the following: 

(a) Compounds of Xe are known but other noble gases do not form compounds 

(b) Giving reason arrange alkali metals in increasing order of first ionization enthalpies

(c) Estimate the first ionization enthalpy values of Mg and Al.

Answer 1

(a) Ionisation energy of Xe is minimum, hence electron can be taken out from it stable noble gas configuration allowing it to make some compounds, 

(b) Li > Na > K > Rb > Cs. Ionisation energy decreases as size increases. As size increases, outermost elements are away from nuclear pull, so electron can be easily removed.

(c) Mg = 700 kJ/mol. Al = 600 kJ/mol.