If k,l and m shells of an atom are completely filled with electrons, the.n what would be:
1. the total no. of electrons in the atom?
​2.find the valency

Number of electrons is 18
Valency =0

As we know that the formula to derive the maximum number of electrons present in a shell is given by 2n², where n is the orbit number.
therefore,
k shell : n=1
so max number of electrons= 2(1)²=2
similarly,
max. number of electrons in;
L shell = 2(2)²=8
M shell= 2 (3)²=18
therefore total number of electrons equals to 18+2+8 that is 28.

sorry it's 18

it's 8+2+8

because the last shell always contains 8 electrons

Total electrons 18 and valency 0

total electrons in the atom=electrons in k shell+electrons in l shell+electrons in m shell
                    =2+8+8
                    =18 electrons.
valency will be zero.

Can u pls explain why 8 and not 18