Two elements 'A' and 'B' belong to the 3rd period of Modern periodic table and are in group 2 and 13 respectively. Compare their following characteristics in tabular form:

Question

Two elements 'A' and 'B' belong to the 3rd period of Modern periodic table and are in group 2 and 13 respectively. Compare their following characteristics in tabular form:
(a) Number of electrons in their atoms

(b) Size of their atoms

(c) Their tendencies to lose electrons

(d) The formula of their oxides

(e) Their metallic character

(f) The formula of their chlorides

Philoid · Accepted Answer

(a) Electronic configuration of A = 2, 8, 2

Electronic configuration of B = 2, 8, 3

(b) Along a period the atomic size of elements decreases. Thus element A has a higher size than B.

(c) Along a period due to increase in effective nuclear charge the tendency to loss electrons decreases, thus A has more metallic character.

(d) Valency of an O atom is -2. Hence formula is A₂ O₂

Valance electrons B atom is 3. Hence formula is B₂O₃

(e) Along a period the metallic character of elements decreases. A is thus more metallic.

(f) Valency of a Cl atom is -1.

Number of valance electrons in A=2 hence ACI₂

Number of valance electrons in B=2 hence BCI₃

Characteristics	A	B
(a) No. of electrons in their atom	4 or 12 or 20	5 or 13 or 13
(b) Size of their atoms	Bigger	Smaller
(c) Their tendencies to lose electrons	More	Less
(d) The formula of their oxides	AO or A₂ O₂	B₂O₃
(e) Their metallic character	More metallic	Less Metallic
(f) The formula of their chlorides	ACI₂	BCI₃