Question

the valence electrons of an element belong to M shell , which period does it belong to​

Answer 1

in M shell their are 6 electron

Answer 2

Element X : M shell= 18 electrons

M shell means n= principal quantum number =4 and N shell = 1 electron.

N shell means n = principal quantum number =4

Therefore, element X=Cu with electronic configuration as :

Cu : 1s 2 2s 2 2p 63s 2 3p 63d 10 4s 1

Other elements of group 11 are Cu (Copper), SIlver (Ag) and Gold (Au).