The elements 4Be, 12Mg and 20Ca, each having two valence electrons, in their valence shells, are in period 2, 3 and 4 respectively

CBSE Class 10 CBSE Class 10 Science
,
1

The elements 4Be, 12Mg and 20Ca, each having two valence electrons, in their valence shells, are in period 2, 3 and 4 respectively of the modern periodic table. Answer the following questions associated with these elements, giving reason in each case:

  1. In which group should they be?
  2. Which one of them is least reactive?
  3. Which one of them has the largest atomic size?
2

1.All three elements have valency 2. Thus, they should be present in group 2 of the periodic table.

2.On going down, a group in the periodic table, the reactivity of an element increases because of decrease in the effective nuclear charge and increases in the atomic size; this makes the removal of valence electrons easy. Thus, among the given elements, 4Be is the least reactive element.

3.On going down, a group in the periodic table, the atomic size of elements increases because of the addition of new shells. Thus, among the given elements, 2QCa has the largest atomic size.