Question

The electronic configurations of four elements A, B, C and D are as follows:

A	2, 8, 1
B	2, 8, 7
C	2, 8, 8
D	2, 4

(a) Which of these elements is a metal?
(b) Which of these elements are non-metals?
(c) Which two elements will combine to form an ionic bond?
(d) Which two elements will combine to form a covalent bond?
(e) Which element will form an anion of valency 1?
(f) Which element is a noble gas?

Answer 1

(a) Element A is metal, as it belongs to the alkali metal group(1) of the modern periodic table.

(b) Element D is a non-metal, as it belongs to the carbon family(14) of the modern periodic table.

(c) An ionic bond is formed by permanent transfer of electrons, so element "A" will lose one electron to achieve noble gas configuration and element "B" will gain an electron to achieve the noble gas configuration. So, ionic bond forms between A and B.

(d) The covalent bond is formed by sharing of electrons, so element "B" requires an electron to achieve the noble gas configuration and "D" requires four electrons to achieve the noble gas configuration. Hence, D will form four single bonds with four molecules of B.

(e) Element "B" will form an anion of valency 1, as it will accept one electron from other donating species.

(f) Element "C" is a noble gas element, as its outer most shell is fully filled.