An element has 2 electrons in the M shell. What is the atomic number of the element ?

Explanation

There are 2 electrons in the M shell. It means that the K shell and L shell, which precede the M shell, are completely filled. The K shell can contain a maximum of 2 electrons and the L shell a maximum of 8 electrons. Thus , the electronic configuration of the element is
`{:(K,L,M),(2,8,2):}`
Hence, the total number of electrons in the atom is equal to
`2+8+2=12`
Atomic number=number of protons =number of electrons =12.