Which of the following elements will form an acidic oxide?
(a) An element with atomic number = 7
(b) An element with atomic number = 3
(c) An element with atomic number = 12
(d) An element with atomic number = 19

Correct answer: (a) An element with atomic number = 7

Explanation: Non-metals form acidic oxides in general. Non-metals have 4 to 8 electrons in the outermost shell. The electronic configuration of given elements are (a) i.e. 7 = 2, 5 (b) i.e. 3 =2, 1 (c) i.e. 12 =2, 8, 2 (d)i.e. 19=2, 8, 8,1.

So, element with atomic number = 7 (electronic configuration = 2, 5) with is non-metal (N) and it will form an acidic oxide.