Question

An element ‘X’ has its electronic configuration of ‘K’ shell $(n-5)s^2$ and the total number of electrons in its outer-most, penultimate and antipenultimate shell are $2,8$ and $25$ respectively, then find out the total number of unpaired electrons in element ‘X’ in its ground state

Answer 1

Answer: 7

For $K$ shell $(n-5)s^2=1s^2$ so value of $n$ is ‘6’
Electronic configuration of ‘X ’
$1s^2$ ______ $4s^2\underset{2}{4p^6}4d^{10}\underset{5}{4f^7}5s^2\underset{8}{5p^6}5d^0\underset{2}{6s^2}$
Unpaired electron is $7$