Question

If elements are given then how we can identify their group number and periods ,which they belong to ???

Answer 1

For finding block-


Electronic configuration - 1s2 2s2 2p6 3s2 3p6 4s2

The last electron enters in the s block , hence the element belongs to the “s” block.

For finding period-

Write the electronic configuration.Highest value of the principal quantum no. will denotes the period no.

(the numerical value written before the block denotes the principal quantum no.)

Eg: atomic no. 16

Electronic configuration- 1s2 2s2 2p6 3s2 3p4

The highest value of principal quantum no.= 3

Hence , the element belongs to

the third period.

For finding group-

Write the electronic configuration.For s block- it is equal to the no. of ele ctrons in the outermost shell.For p block- it is equal to the no. of electrons in the outermost shell + 10.For d block- it is equal to the no. of electrons in the outermost shell + no. of electrons in the penultimate shell.

Eg: atomic no. - 12, 21, 7

Electronic configuration- 1s2 2s2 2p63s2

Last electron enters in the s block .

Hence, group no.= 2

Electronic configuration- 1s2 2s2 2p6 3s2 3p6 3d1 4s2

Last electron enters in the d block( first 4s is filled then 3d).

Hence group no.= 2+1=3

Electronic configuration =1s2 2s2 2p3

Last electron enters in the p block .

Hence , group no.= 5+10=15.

Answer 2

hlw mate ,
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ur answer ,
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hlw, their is a trick to find them my chemistry teacher told me about this ...

TRICK : PERIODS = NUMBER OF SHELL

GROUP NUMBER = VALENCE ELECTRON +10

VALENCE ELECTRON MEANS THE TOTAL NUMBER OF ELECTION IN THE OUTERMOST SHELL