Electronic configuration and position of elements

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.

-:-:-:-

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.

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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