The outer electronic configuration is ns2np′, i.e. the element belongs to group 13 (boron family). As the element in crystalline form is unreactive towards oxygen, it might be boron which does not react with air in crystalline form. In amorphous form it reacts to form B2O3. Boron trioxide which is acidic in nature. Down the group the nature of oxide changes from acidic to amphoteric (Al2O3. and gallium oxide) to basic (indium and thallium oxide). Thus, given element is boron.