Question

Which of the following terms is not correct for hydrogen?
A. Its molecule is diatomic.
B. It exists both as H⁺ and H^- in different chemical compounds.
C. It is the only species which has no neutrons in the nucleus.
D. Heavy water is unstable because hydrogen is substituted by its isotope deuterium.

Answer 1

Hint: In this question we will use the properties of hydrogen to find which of the following terms is not correct for hydrogen. We will use properties like atomicity, the isotope and the oxidation state of hydrogen in different compounds.

Complete Step by Step Answer:
Hydrogen is a monatomic atom. Since hydrogen only has one electron, it can only create diatomic molecules. As far as we are aware, atoms never exist in a free state; instead, they are constantly present as molecules. Therefore, hydrogen also exists as a diatomic molecule under normal conditions.

The single electron in the valence shell (1s¹) of hydrogen can be easily lost, allowing for the existence of the H⁺ ion. To achieve a stable structure, it can also accept one electron from outside, leading to its existence as H^-.

Hydrogen, an atom with only one proton, does not require any neutrons to be stable, in contrast to other elements. Since hydrogen only contains one proton, there is no proton-proton repulsion and hence no requirement for neutrons.

Deuterium oxide, sometimes known as heavy water (D₂O), is a compound that contains two deuterium atoms and one oxygen atom. Due to the extra neutron present in its nucleus, deuterium is a stable isotope of hydrogen that has twice the mass of hydrogen and does not decay. Hydrogen and compounds containing hydrogen, such as water and hydrocarbons, include deuterium.
The correct answer is D.

Note: Heavy water might seem like it is unstable as it is made from the isotope of Hydrogen. But the neutron present in Deuterium stables the compound and thus it is used as moderator in nuclear reactors.