Group the following electron configurations in pairs that would represent similar chemical properties at their atoms;
a. 1s2 2s2 2p6 3s2
b. 1s2 2s2 2p3
c. 1s2 2s2 2p6 3s2 3p6 4s2 3d104p6
d. 1s22s2
e. 1s2 2s2 2p6
f. 1s2 2s2 2p6 3s2 3p3

Pairs are:  (a) and (d), (b) and (f), (c) and (e)

Explanation:

In a periodic table, elements are arranged in 18 vertical columns known as groups and 7 horizontal rows known as periods.

Elements arranged in a group show similar chemical properties because of the presence of same number of valence electrons.

Valence electrons are defined as the electrons which are present in the outermost shell of an atom. Outermost shell has the highest value of 'n' that is principal quantum number.

For the given options:

The given electronic configuration is:  

The number of valence electrons in the given configuration are 2

The given electronic configuration is:  

The number of valence electrons in the given configuration are [2 + 3] = 5

The given electronic configuration is:  

The number of valence electrons in the given configuration are [2 + 6] = 8

The given electronic configuration is:  

The number of valence electrons in the given configuration are 2

The given electronic configuration is:  

The number of valence electrons in the given configuration are [2 + 6] = 8

The given electronic configuration is:  

The number of valence electrons in the given configuration are [2 + 3] = 5

Electronic configuration of (a) and (d) will form a pair, (b) and (f) will form a pair, (c) and (e) will form a pair and will have similar chemical properties.

Hence, the pairs are:  (a) and (d), (b) and (f), (c) and (e)