Question

Which of the following explanation is best for not placing hydrogen with alkali metals or halogen
A. The ionisation energy of hydrogen is high for group of alkali metals or halogen
B. Hydrogen can form compounds
C. Hydrogen is a much lighter element than the alkali metals or halogens
D. Hydrogen atom does not contain any neutron

Answer 1

Hint: In this question we will use the properties like, ionisation energy, electronic configuration, electron affinity and the behaviour as a reducing or oxidising agent of alkali, halogens and hydrogen to find a proper reason as to why hydrogen should not be placed with alkali metals or halogen.

Complete Step by Step Answer:
Ionisation energy: There is just one orbital in hydrogen, and it is strongly drawn to the nucleus. It is therefore much smaller than the alkali metal and has a higher ionisation enthalpy as a result. Whereas, halogens and hydrogen both produce anions because they lack one electron needed for stable conformation. Each of them is monovalent and electronegative.

Electron Affinity: Hydrogen's electron affinity value is much more similar to alkali metals than halogens. This is because hydrogen and the other alkali metals only have one valence electron. Halogens need one electron to achieve a stable noble gas electronic configuration, but alkali metals are more easily able to donate one electron and do so. Alkali metals and hydrogen have a weak affinity for electrons.

Electronic Configuration: The electronic configuration of hydrogen is 1s¹ which is similar to the outermost electronic configuration of alkali metals (ns¹) whereas the electronic configuration of halogens is ns²np⁵.

Therefore, the best explanation for not placing hydrogen with alkali metals and halogens is that hydrogen is a much lighter element than the alkali metals or halogens
The correct answer is C.

Note: Hydrogen does not contain neutrons is a true sentence but is not the best explanation as to why it is not placed with alkali metals or halogens. Hydrogen is the only element that contains only protons and electrons. Hydrogen can form compounds just like alkali metals and halogens so that statement also justifies nothing.