Question

Considering reactivity series, which one is least active?

• A. $Ar$
• B. $O$
• C. $S$
• D. $Ti$
• E. $U$

Answer 1

The correct option is A $Ar$

Considering reactivity series, Ar is least active.
Ar is a noble gas in which it has completed its octet. The completely filled valence shell provides extra stability and hence, Ar has no tendency to react and is chemically inert.
The electronic configuration of Ar (Z=18) is $1s^2{s}^{2}2p^{6}3s^{2}3p^6$.
S (Z=16) has the electron configuration $1s^2{s}^{2}2p^{6}3s^{2}3p^4$.
The electronic configuration of O (Z=8) is $1s^2{s}^{2}2p^4$.
The electronic configuration of Ti (Z=22) is $1s^2{s}^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^2$ .
The electronic configuration of U (Z=92) is $\left[Rn\right]5f^{3}6d^{1}7s^2$.