Question

Which of the following is correct for hydrogen
A. It can form bonds in +1 as well as -1 oxidation state
B. It is always collected at the cathode
C. It has a very high ionisation potential
D. It has the same electronegativity as halogens

Answer 1

Hint: In ionic compounds, hydrogen acts as an anion which is known as a hydride. The electronegativity of hydrogen is 2.2 whereas the electronegativity of fluorine, and chlorine are 3.98 and 3.16 respectively.

Complete Step by Step Answer:
In this question, we are given statements about hydrogen and we have to figure out which is correct.
A. It can form bonds in +1 as well as -1 oxidation state
The oxidation state of an atom is the theoretical charge that will be carried by that atom if all of the bonds formed by the compound of that atom are completely ionic.
When hydrogen combines with metals, it forms metallic hydrides. The oxidation number of hydrogen, in this case, is -1.
This is because metals have lower electronegativity than hydrogen. They lose electrons easily to form cations.
So, hydrogen gains the electron and has a -1 oxidation state.
When a nonmetal reacts with hydrogen, it acquires a +1 oxidation state.
For example, when it is combined with a nonmetal as in C, N, O and Cl.
This is because nonmetals have higher electronegativity than hydrogen.
So the nonmetal takes an electron from the hydrogen.
So, hydrogen can form bonds in +1 as well as -1 oxidation states.

B. It is always collected at the cathode
Electrolysis of water is the decomposition of water liberating hydrogen and oxygen gases by using an electric current.
In this case, hydrogen gas is liberated at the cathode. This is because in this case, hydrogen exists as H⁺, thus undergoing reduction at cathode.
If we do the electrolysis of Sodium hydride, we can get hydrogen gas at the anode. In this case, it exists as H^-, thus undergoing oxidation at anode.
So, hydrogen is collected at cathode and anode as well.
So, B is incorrect.

C. It has a very high Ionisation potential
Ionisation potential is defined as the energy needed to extract the outermost shell electron of an isolated gaseous atom.
Hydrogen has only one electron which can be easily lost. So, hydrogen has low Ionisation potential.
So, C is incorrect.

D. It has the same electronegativity as halogens
Electronegativity is defined as the capacity of an atom to attract electrons towards itself.
The electronegativity of halogens is very high. This is because they need only one electron to complete their octet. So, they attract electrons towards themselves.
Hydrogen has low electronegativity because of its small size.
So, hydrogen doesn't have the same electronegativity as halogens.
So, D is incorrect.

So, option A is correct.

Note: Ionisation energy is an estimate of the energy required to draw a particular electron away from the appeal of the nucleus. An increased value of Ionisation energy demonstrates an increased attraction between the electron and the nucleus. Attraction declines with distance. An electron close to the nucleus will be more intensely attracted than an electron which is distant.