Question

Number of neutrons in a heavy hydrogen atom is:
(A) 0
(B) 1
(C) 2
(D) 3

Answer 1

Hint: Heavy hydrogen is one of the isotopes of the hydrogen atom. We can obtain the number of neutrons present in the atom if we know its atomic number and its atomic weight.
Number of neutrons = Atomic weight – Atomic number

Complete step by step solution:
We need to find the number of neutrons present in the heavy hydrogen atom. Let’s know what is meant by heavy hydrogen.
-Hydrogen atoms have three isotopes. The three isotopes are known as Hydrogen, Deuterium and Tritium.
-Hydrogen, Deuterium and Tritium have the atomic mass of 1, 2 and 3 $gmmo{l^{ - 1}}$ respectively.
-Isotopes are the species in which the number of protons present in the element is the same but its atomic weight is not the same.
-Now, Deuterium is also known as heavy hydrogen as its atomic mass is $2gmmo{l^{ - 1}}$ and this is heavier than a normal hydrogen atom.
-We know that the weight of the atom is mainly due to the protons and the neutrons present in them. The weight of the electrons is so less that we can ignore them in the process of calculating the weight of the atoms.
We know that
Number of neutrons = Atomic weight – Atomic number
-So, as the atomic weight of Deuterium is $2gmmo{l^{ - 1}}$, it should have one neutron because one proton is already there in its structure (its atomic number is 1).
-Normal hydrogen does not have any neutron in its structure and Tritium has two neutrons while the number of protons remains the same in all the isotopes.
Thus, we can conclude that there is one neutron and one proton present in a heavy hydrogen atom.

So, the correct answer is (B).

Note: Remember that Deuterium is considered as the heavy hydrogen. Actually, Tritium is also an isotope of the hydrogen atom and it is heavier than Deuterium as well. The natural abundance of Hydrogen and Deuterium is 99.98%, 0.02% and Tritium is found in trace amounts.