Question

Which of the following two elements belong to (i) the same group (ii) same period in the periodic table 4^Be ; 3^Li; 12^Ms, 35^Br

Answer 1

Principal quantum number of outermost electron in Be and Li is 2. Hence both Be and Li belong to the same period i.e., 2^nd period. Be and Mg have the same number of outermost electrons, i.e., 2. Hence both Be and Mg belong to the same group in the periodic table.