Question

Which of the following is/are example(s) of isotones?
A. $_6{C^{12}}$ and $$_6{C^{13}}$$
B. $$_{11}N{a^{23}}$$ and $$_{12}M{g^{23}}$$
C. $$_{14}S{i^{30}}$$ and $$_{16}{S^{32}}$$
D. $$_{83}B{i^{210}}$$ and $$_{84}P{o^{210}}$$

Answer 1

Hint: All atoms consist of electrons, neutrons and protons. They also consist of sub-atomic particles such as muon, up quark and many more. A similarity is observed between the numbers of electrons, protons and neutrons. Isotones is one such similarity. Atoms which have the same number of neutrons are called isotones.

Complete step by step answer:
Atoms are the fundamental unit of a matter. Majority of the mass in an atom is found in the nucleus. Atoms are composed of nuclei which are at the center of the atom. We have protons and neutrons with other subatomic particles in the nucleus.
The atomic number of an element is denoted by Z. Mass number of an element is denoted by A. The atomic number is the number of electrons or number of protons present in an atom while atomic mass number is the sum of masses of nucleons.
We have $A = Z + N$
Where N is the number of neutrons,
$$ \Rightarrow N = A - Z$$
Atoms that have the same number of neutrons are called isotones.
Thus, atoms having the same $$A - Z$$ values are called isotones.
For $_6{C^{12}}$ (atomic mass is $$12$$ ), number of neutrons is $$12 - 6 = 6$$
and $$_6{C^{13}}$$ (atomic mass is $$13$$ ), number of neutrons is $$13 - 6 = 7$$
Number of neutrons is different; they are not isotones.
Option A is incorrect.

For $$_{11}N{a^{23}}$$ number of neutrons is $$23 - 11 = 12$$
And $$_{12}M{g^{23}}$$ number of neutrons is $$23 - 12 = 11$$
Number of neutrons is different; they are not isotones.
Option B is also incorrect.

For $$_{14}S{i^{30}}$$ number of neutrons is $$30 - 14 = 16$$
And $$_{16}{S^{32}}$$ number of neutrons is $$32 - 16 = 16$$
Number of neutrons is the same; they are isotones.
Option C is correct.

For $$_{83}B{i^{210}}$$ number of neutrons is $$210 - 83 = 127$$
And $$_{84}P{o^{210}}$$ number of neutrons is $$210 - 34 = 126$$
Number of neutrons is different; they are not isotones.
Option D is also incorrect.

As a result, only option C is correct.

So, the correct answer is “Option C”.

Note:
Atomic pairs are classified in following types: Isobars, isotones, isomers.
In isobars the pair of atoms have the same A.
For isotopes have the same Z but different N.
Isomers have the same Z but in different excited states.
In isodiaphers have same N-Z values
In isotones have the same N but different Z.