An element ' $M$ ' has $50 \%$ of the electrons filled in the $3{ }^{ ext {rd }}$ shell as in the $

Question

An element ' $M$ ' has $50 \%$ of the electrons filled in the $3{ }^{	ext {rd }}$ shell as in the $2^{	ext {nd }}$ shell. The atomic number of ' $M$ ' is\

Professor PC Thomas Classes · Answer

(c) Since, the 3$^{rd}$ shell has 50% of electrons as in 2$^{nd}$ shell, it means 1$^{st}$ and 2$^{nd}$ shell of elements are  completely filled. As  2$^{nd}$ shells contains maximum of 8 electrons, its 50% would b3 4. Thus, the electronic configuration of element 'M' will be 2,8,4 and its atomic number will be 14