Question

(a) What are ‘groups’ and ‘periods’ in the periodic table? 

(b) Two elements M and N belong to groups I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary? 

(i) Sizes of their atoms. 

(ii) Their metallic characters. 

(iii) Their valencies in forming oxides. 

(iv) Molecular formula of their chlorides.

Answer 1

(a) The vertical column in the periodic table are called ‘groups’, the horizontal rows in the table are called periods. 

(b) (i) ‘M’ and ‘N’ belong to the same period but group I and II respectively. N is smaller than M as the atomic size decreases on moving from left to right across the periodic table. 

(ii) M is more metallic than ‘N’ because metallic character decreases from left to right as tendency to lose electrons decreases due to decrease in atomic size. 

(iii) The valencies of M and N are 1 and 2 respectively, valency across the period first increases then decreases. 

(iv) MCl and NCl₂.