Question

The elements Li, Na and K each having one valence electron, are in period 2, 3 and 4 respectively of modern periodic table.
(i) In which group of the periodic table should they be?
(ii) Which one of them is least reactive ?
(iii) Which one of them has the largest atomic radius ?
Give reason to justify your answer in each case

Answer 1

Explanation:

(i)They are in group 1 because all the elements in a group have 1 valence electron. They form positively charged ions by losing one electron.  

(ii) Lithium is least reactive because the reactivity of an element depends upon the ability of its atoms to donate or accept electrons.  

(iii) Potassium will have the largest atomic radius rule to the addition of a new shell. Atomic size generally increases from top to bottom in a group.

Answer 2

Answer:

[i] Since the elements have one valence electron, they are placed in group 1 (Alkali metals) in the order Li (period = 2) , Na (period = 3) , K (period = 4).

(b) Since the reactivity of the elements increases down a group, the element Li is the least reactive chemically.

[iii] K has larger radius as it has more no. of shells than Li and Na.

Explanation:

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