Question

Why in the attachment period is taken as 4 and not 3 as the last orbital is $\bf 3d^{2}$

Please any one clear my doubt regarding this by giving some more additional information.

Best answer = BRAINLIEST.​

Answer 1

Well ,if u have this doubt,then understand one thing,that ur basic is not clear

Explaination (of above doubt):-Period ,actually shows the number of shells that electron have.

Examples

1)Hydrogen and helium:-Electronic configuration of H is 1s1,

or 1

it means it has only one shell,which have only one electron.

As it has one shell so,it is in first period

similarly helium electronic configuration:-2 or 1s2

this means it have one shell which have 2 electron,so it is also in first period

2) Nitrogen:-

electronic configuration,:-2,5 or 1s2 2s2,2p4

It shows that it have 2 shells , that's why it is in second period

if we see configuration of above element

Element of 22 atomic no. have electronic configuration:-1s2,2s2,2p6,3s2,3p6,4s2,3d2

4s2 shows that,it have 4 shells

so,it will be in fourth period as like above examples

Answer 2

$\mathcal{\gray{\underbrace{\blue{GIVEN:-}}}}$

• Element - [22]

• 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²

• Period :- 4

• Block :- d

• Group :- 4

$\mathcal{\gray{\underbrace{\blue{TO\: FIND:-}}}}$

• Why ‘22’ no. Element taken as 4th period as the last orbital is 3d² ?

$\mathcal{\gray{\underbrace{\blue{SOLUTION:-}}}}$

⚡ The name of the element whose Element no. 22 is Titanium [Ti] .

✍️ As we write the electronic configuration of Ti,

• 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d²

⚡ The above electronic configuration was obeyed the “AUFBAU PRINCIPLE” .

AUFBAU PRINCIPLE :- This principle explains how electrons fill low energy orbitals before they fill higher energy ones .

☞ Plz see the above attached diagram, that summaries the energies of the orbitals upto the 4p level .

⚡ The oddity is the position of the 3d orbitals, which are shown at a slightly higher level than the 4s .

⚡This means that the 4s orbital which will fill first, followed by all the 3d orbitals and then the 4p orbitals .

✍️ But if you consider the period of an Element, you follow the following rule .

$\blue\bigstar\:\rm{\pink{\boxed{\purple{Period\:of\:an\:Element\:=\:No.\:of\:\bold{principle\:quantum}\:\atop{number\:of\:the\:valence\:shell}\:}}}}$

Hence,

⚡ In the electronic configuration of Ti, the Principle quantum number is 4 .

✩ Therefore, the period of Ti is 4 .

MORE INFO :-

For prediction of BLOCK :-

• To check, in which orbital the element receives the last electron .

For prediction of Group :-

$\orange\bigstar\:\rm{\pink{\boxed{\red{Group\:number\:=\:No.\:of\:electrons\:in\:penultimate\:\atop{shell\:+\:valence\:shell\:}}}}}$