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 of the atom of this element. This means that the K and L shells of the atom of this element (which come before M shell) are completely filled with electrons. Now, K shell can accommodate 2 electrons, L shell can accommodate 8 electrons adn we have been given that M shell has 2 electrons. So, the electronic configuration of this element becomes 2,8,2. Thus, the number of electrons in its aton is `2 + 8 + 2= 12`. Since the number of electron in a neutral atom is equal to the number of protons, therefore, the atomic number of this element is 12.