the only possible answer i have is the elements which have no. of occupied shells as 3 are only 8 elements till date discovered i.e Na, Mg, Al, Si, P, Cl, Ar and period no. 3 includes the elements with no. of occupied shells 3 and hence there are only 8 of them. thus period 3 has 8 elements only. if any other answer plz tell me!
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You are right as no. of shells = their period number.
If you know about electronic configuration then according to it
the elements are divided into shell
so the 1 shell=max 2 electron
2 shell= max 8 electron
3 shell= max 8 electron
4 shell= max 8 electron
5 shell = max 18 elements and so on
therefore the first group of elments have 1 shell so it is called as 1 period and has one element as position of hydrogen is not fixed.
second, third contains 8 electron and remaining other contains 18 electrons as accordin to their valence shells but the middle elements also called transition elements are not included while calculating the basic electronic configuration. This table was made to arrange the elements accordin to their properties.
If you know about electronic configuration then according to it
the elements are divided into shell
so the 1 shell=max 2 electron
2 shell= max 8 electron
3 shell= max 8 electron
4 shell= max 8 electron
5 shell = max 18 elements and so on
therefore the first group of elments have 1 shell so it is called as 1 period and has one element as position of hydrogen is not fixed.
second, third contains 8 electron and remaining other contains 18 electrons as accordin to their valence shells but the middle elements also called transition elements are not included while calculating the basic electronic configuration. This table was made to arrange the elements accordin to their properties.