Question

prediction the period , group and block of cr(z=24)​

Answer 1

Answer:

11th

Chemistry

Classification of Elements and Periodicity in Properties

Electronic Configuration of Elements in Periodic Table

How can u predict the group...

CHEMISTRY

How can u predict the group, period and block of an element? Explain with examples.

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ANSWER

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 = 1s

2

2s

2

2p

6

3s

2

3p

5

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

Explanation:

Answer 2

Answer:

Z =29 is the answer.....