Question

Consider the following elements:
Ca, Cl ,Na, I, Li, Ba, Sr, K, Br
Separate these elements into three groups (families) of similar properties. State one property in each case on the basis of which you have made your choice.

Answer 1

Hint: Na,Li and K are alkali metals and Ca, Ba and Sr are alkaline earth metals and both theses metals comes under the category of s-block elements whereas Cl, Br and I are halogens and comes under the category of p-block elements and on the basis of their outer electronic configuration, we can classify them into their respective groups and families. Now you can easily answer the given statement.

Complete answer:
Na stands for sodium, Ca stands for calcium, Cl stands for chlorine, I stands for iodine , Li stands for lithium, Ba stands for barium, Sr stands for strontium, K stands for potassium and Br stands for bromine.
Lithium, Sodium, calcium, barium, potassium and strontium are metals whereas chlorine, bromine , iodine are non-metals.
Now considering the statement as;-
Lithium , sodium and potassium all are alkali metals belonging to the group 1 of the periodic table and come under the category of s-block elements. Elements belonging to the same group has the same outer electronic configuration and for s-block elements it is \[n{{s}^{1}}\]and the outer electronic configuration of Li is \[2{{s}^{1}}\], Na is \[3{{s}^{1}}\]and potassium is \[4{{s}^{1}}\].
Calcium , strontium and barium all are alkaline earth metals belonging to the group 2 of the periodic table and come under the category of s-block elements. Elements belonging to the same group has the same outer electronic configuration and for group2 elements it is \[n{{s}^{2}}\]and the outer electronic configuration of Ca is \[4{{s}^{2}}\], Sr is \[5{{s}^{2}}\]and Ba is \[6{{s}^{2}}\].
Chlorine, bromine and iodine all are halogens belonging to the group 17th of the periodic table and comes under the category of p-block elements. Elements belonging to the same group has the same outer electronic configuration and for group 17th elements it is \[n{{s}^{2}}n{{p}^{5}}\]and the outer electronic configuration of Cl is \[3{{s}^{2}}3{{p}^{5}}\], Br is \[4{{s}^{2}}4{{p}^{5}}\]and for I is \[5{{s}^{2}}5{{p}^{5}}\].

Note:
- Always remember that the s-block element has a strong tendency to lose electrons to acquire stable electronic configuration of the nearest noble gas but p-blocks have a strong tendency to gain electrons to complete its octet and to acquire stable electronic configuration of the nearest noble gas.