Question

Question.14 (a) Which two criteria did Mendeleev use to classify the elements in his Periodic

Table?

(b) State Mendeleev’s periodic law.

(c) Why could no fixed position be given to hydrogen in Mendeleev’s Periodic Table?

(i) Sizes of their atoms

(ii) Their metallic characters

(iii) Their valencies in forming oxides

(iv) Molecular formulae of their chlorides

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

periodic table are called ‘periods’.

(b) (i) ‘M’ and ‘N’ belong to same

period but group I and II. Therefore, ‘N’ will be smaller than ‘M’ as atomic size goes on

decreasing from left to right.

(ii) ‘M’ is more metallic than ‘N’. Metallic character goes on decreasing from left to right as

tendency to lose electrons decreases due to decrease in atomic size.

(iii) Their valencies are 1 and 2 respectively in forming oxides. Valency goes on increasing first

and then decreases.

(iv) MCI, NCI2 are molecular formulae of their chlorides.

(d) How and why does the atomic size vary as you go

(i) from left to right along a period?

(ii) down a group?​

Answer 1

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