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how we find what's the group and period of an element? Explain with example. please answer tomorrow is my exam​

Answer»

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Prediction of PERIOD ⟶ In the electronic configuration of an atom, the principal quantum number (n) of the valence electrons represents the period of an element.

Prediction of Block ⟶ The orbital out of s,p,d and f which receives the last electron represents the block of an element

Prediction of Group ⟶ The group prediction occurs with the HELP of block as:-

(1) For s block: Group Number = Number of valence e−

(2) For d block: Group Number = Number of e− in (n−1)d subshell + number of e− in ns subshell

(3) For p block: Group Number = Number of valence e−+10

(4) For f-block: Group Number = 3 (always)

For EXAMPLE for chlorine with Z=17

Electronic configuration = 1s²2s²2p⁶3s²3p⁵

Since the last e− enters in p - subshell:

(i) ∴ Block will be ′p′

(ii) For group we have element in p-block

∴ Group number = 10+ Valence e− in s subshell + Valence e− in p subshell

Group Number = 10+2+5=17

(iii) For period

The quantum number of valence e−=3

∴ Period number = 3


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