Q9 of 60 Page 1

The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table.

Answer the following questions, giving justification in each case:


(i) Write the group to which these elements belong.


(ii) Name the least reactive element.


(iii) Name the element having largest atomic radius.

The electronic configuration, outermost electrons in elements Be, Mg and Ca can be written as follows and the electronic configuration can be funded out:


(i)Since all the elements belongs to 2nd group, so they all will have 2 valence electrons.


(ii) As we know, reactivity of metals increases as move from left to right in a period due to increase in the tendency to lose electrons in a group. Since Be is smallest among all elements and the forces of attraction between nucleus and electrons will be high, due to which the valence electrons can’t be removed. Therefore, Be is the least reactive metal.


(iii) Since Ca has maximum no. of shells i.e. 4, so It will have largest atomic radius.


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