Question

Elements with atomic numbers 9, 17, 35, 53 are collectively known as:

• A. chalcogens
• B. halogens
• C. lanthanides
• D. rare gases

Answer 1

The correct option is B halogens

Elements having the atomic number:

9 is fluorine: $\left(He\right)2s^{2}2p^5$
17 is chlorine: $\left(Ne\right)3s^{2}3p^5$
35 is bromine: $\left(Ar\right)4s^{2}4p^5$
53 is iodine: $\left(Kr\right)5s^{2}5p^5$

We can observe here that all these elements having the general electronic configuration of $n{s}^{2}n{p}^5$, hence these elements belong to ${17}^{th}$ group elements.