(a) The element with electronic configuration 2, 8, 7 will form ionic bonds with metals and with non-metal it will form covalent bond.
(b) The element with electronic configuration is 2, 8, 4 is Si and with chloride it forms SiCl4.
(c) The alkaline earth metal in the period 3 is Mg and it’s oxide is basic in nature (i.e. MgO is basic is nature).
(e) The number of electrons in the penultimate shell of the element with valency -1 is 8.
(e) The element is Magnesium and electronic configuration is (2, 8, 2)