Question

An atom with atomic number $20$ is most likely to combine chemically with the atom whose atomic number is___________.

• A. $11$
• B. $16$
• C. $18$
• D. $10$

Answer 1

Answer: (B)

$16$

Atomic number $20$ will be distributed in electron shell as $2,8,8,2$.

Its valency is $2$. It will loose this $2$ electron to gain stability and noble gas configuration. If atomic number $11$ is distributed in electron shell it will be $2,8,1$.

Atom with valence electron $1$ will loose this atom to gain stability. Hence, both ${}_{20}X$ & ${}_{11}X$ will gain nothing i.e. will not gain stable electronic configuration after combining with each other.

An atom with atomic number $16$ has electronic configuration as $2,8,6$.It will gain $2$ electron from ${}_{20}X$ and complete its octet. Thus atom having atomic number $20$ will combine most likely with atom having atomic number $16$ as both will gain stable electronic configuration.