Question

The atoms of different elements having the same number of neutrons is known as:
A.Isobars
B.Isomers
C.Isotones
D.Isotopes

Answer 1

When encountering such terms like ‘isobars’, we must understand what they mean. The word ‘iso’ stands for the same. To solve this question, we will first understand the definition of each term mentioned and then interpret the correct option.

Complete step by step answer:
Isotopes are defined as the group of the same elements that have different numbers of neutrons but the same number of protons and electrons.
Example – The isotopes of Hydrogen are – ${^1_1}H$ - Protium, ${^2_1}H$ - Deuterium and ${^3_1}H$ - Tritium.
Isomers are molecules that have the same molecular formula but different structural formula.
Example – The isomers of butane are –

Isotones are a group of atoms of different elements that have the same number of neutrons but different number of protons.
Example – Oxygen ${_8^{16}}O$ , Nitrogen ${^{15}_7}N$ and Carbon ${^{14}_6}C$ have same number of neutrons, i.e., 8. Hence, they are called isotones.
Isobars are different elements that have different atomic numbers but have the same mass number.
Example – An example of pair of isobars is $^{40}S{,^{40}}Ca{,^{40}}K{,^{40}}Ar{,^{40}}Cl$ .
Hence, the correct answer is (C) i.e., isotones.

Note: In a given pair of isotones, the element with the higher atomic number, would have the higher atomic mass number out of the two. This tells us that the mass of the element with the higher atomic number would be higher. So, this gives us more information about isotones.