Question

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electronic shells but different number of electrons in their outermost shells. It was found that elements A and G combine to form an ionic compound which can also be extracted from sea water. Oxides of the elements A and B are basic in nature while those of E and F are acidic.
The oxide of element D is almost neutral. Answer the following questions based on the information given herein:
(a) To which group or period of the periodic table do the listed elements belong?
(b) Which one of the eight elements is likely to be a noble gas?
(c) Which one of the eight elements would have the largest atomic radius?
(d) Which two elements amongst these are likely to be non-metals?
​(e) Which one of the these eight elements is likely to be a semi-metal or metalloid?

Answer 1

(a) A and G form an ionic compound so A must be a metal of group 1 and G must be a non-metal of group 17. As the ionic compound of A and G is obtained from seawater so that ionic compound must be sodium chloride. Therefore, A and G belong to the third period of the periodic table.

(b) Because all the given elements belong to the third period and H being the last element of the third period will be the noble gas.

(c) A belongs to the first group of the periodic table, so it has the largest radius.

(d) Oxides of E and F are acidic in nature, so they are non-metals.

(e) The oxide of D is almost neutral, so it is a metalloid.