AIIMS 2013 Chemistry Question Paper for free online practice with solutions

Na, Mg, Al and Si are in period 3 and as we move across the period, the atomic size decreases and hence ionisation enthalpyincreases. So, the order is Na < Mg < Al < Si Hence, IE of Al is greater than that of Mg (737 kj/mol) and lower than that of Si (776 kj/mol).