Q20 of 30 Page 196

Which one has larger atomic size– Cl or Br? Why?

Br has larger atomic size than Cl because the atomic size increases from top to bottom in a group. From top to bottom in a group, the number of shells increases. So, the atomic size increases.


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18

Why is K more reactive than Li?

 19

Why He, Ne and Ar called inert gas?

 21

Where in period 3 of the modern periodic table do we find:

(a) non-metals?


(b) elements forming negative ions?


(c) elements with high melting points?


(d) elements forming positive ions?


(e) metals?


(f) elements with low boiling points?


Mention their atomic numbers only.

 22

An element belongs to 4th period and group 17 of the periodic table. Find out:

(a) the number of valence electrons.


(b) is it a metal or non-metal.


(c) the name of the element.


(d) formula of its compound with hydrogen.


(e) electron dot structure of this element with calcium.