Question

The least reactive element among the following is

• A. ${}_9{X}^{19}$
• B. ${}_{18}{Y}^{16}$
• C. ${}_{11}{X}^{23}$
• D. ${}_{12}{Y}^{24}$

Answer 1

The correct option is B ${}_{18}{Y}^{16}$

The least reactive element among the following is ${}_{18}{Y}^{16}$. The atomic number 18 is of a noble gas with electronic configuration $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$. Since it has completed its octet, it is stable and least reactive.