The atomic numbers of three elements A, B, and C are given below:Element Atomic number
(i) Which element belongs to group 18?
(ii) Which element belongs to group 15?
(iii) Which element belongs to group 13?
(iv) To which period/periods do these elements belong?"
(i) Element C belongs to group 18 as its electronic configuration of element C (10) = 2,8
(ii) Element B belongs to group 15 as its electronic configuration of element B (15) = 2,8,5
(iii) Element A belongs to group 13 as its electronic configuration of element A (5) = 2,3
(iv) The elements A, B, and C all belong to period 2 because all three have the same valence shell filled, i.e, the L shell.
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