Question

Why in the attachment period is taken as 3 and not 4 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.

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Answer 1

Answer:

in a modern periodic table the horizontal rows are known as periods and vertical rows are known as groups . for finding period of an element you should simply see the highest occupied shell in electronic configuration. in the given configuration highest occupied shell is 4 so the element belongs to 4th period

as according to afbaus principle in the given configuration the last electron enters into d orbital thus it belongs to d block

by comparing the valence electronic config. we can say that the element belongs to 4th group

Answer 2

Explanation:

element 22

4s2 , 3d2

this is because 4s is less than 3d .

4s has less energy

in k shell has one subshell= 1s

L shell has= 2s2 and 2p6

M shell has three subshells they are 3s2, 3p6, and 3d10,

N shell has 4s2 , 4p6, 4d 10 ...

1s<2s<2p<3s<3p<4s<3d<4p

Example: athomic number of SC is 21

sub shell electronic configuration is -:

1s2, 2s2 , 2p6, 3s2, 3p6, 4s2, 3d1

To find the group of an element is

s block- group number is the number of last s electron

p block- group number is obtained when 12 is added to the number of last (s+p) electrons

d block- group number is the sum of the last s electron and d electron in the penultimate