Example 3.1: Identifying the group and period of following elements on the basis of
electronic configuration.
Solution
n = 1 for K
n = 2 for L
n = 3 for M (valence shell)
No. of electrons in valence shell= 3
Hence,
Period number = ‘n’ value for valence shell
Period number = 3
Group number = No. of electrons in valence shell
Group number = 3
So, Al is present in 3rd period and 3rd group.
-:-:-:-
i.
n = 1 for K
n = 2 for L (valence shell)
No. of electrons in valence shell= 3
Hence,
Period number = ‘n’ value for valence shell
Period number = 2
Group number = No. of electrons in valence shell
Group number = 3
So, B is present in 2nd period and 3rd group.
-:-:-:-
ii.
n = 1 for K
n = 2 for L
n = 3 for M (valence shell)
No. of electrons in valence shell= 2
Hence,
Period number = ‘n’ value for valence shell
Period number = 3
Group number = No. of electrons in valence shell
Group number = 2
So, Mg is present in 3rd period and 4th group.
Self Assessment
Identify the group and period of the following elements on the basis of electronic configurations.
Solution.
i.
n = 1 for K
n = 2 for L
n = 3 for M (valence shell)
No. of electrons in valence shell= 4
Hence,
Period number = ‘n’ value for valence shell
Period number = 3
Group number = No. of electrons in valence shell
Group number = 4
So,
Si is present in 3rd period and 4th group.
:-:-:-
ii.
n = 1 for K
n = 2 for L
n = 3 for M (valence shell)
No. of electrons in valence shell= 6
Hence,
Period number = ‘n’ value for valence shell
Period number = 3
Group number = No. of electrons in valence shell
Group number = 6
So, Si is present in 3rd period and 6th group.
-:-:-:-
iii.
n = 1 for K
n = 2 for L (valence shell)
No. of electrons in valence shell= 7
Hence,
Period number = ‘n’ value for valence shell
Period number = 2
Group number = No. of electrons in valence shell
Group number = 7
So,
Si is present in 2nd period and 7th group.
:-:-:-
iv.
n = 1 for K
n = 2 for L
n = 8 for M (valence shell)
No. of electrons in valence shell= 8
Hence,
Period number = ‘n’ value for valence shell
Period number = 3
Group number = No. of electrons in valence shell
Group number = 8
So, Ar is present in 3rd period and 8th group.
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