Question

Nuclei of isotopes differ in:
A. Number of protons
B. Number of neutrons
C. Number of neutrons and protons both
D. None of these

Answer 1

The three naturally occurring isotopes of the carbon atom is ${}^{{\rm{12}}}{\rm{C,}}\;{}^{{\rm{13}}}{\rm{C}}\;{\rm{and}}\;{}^{{\rm{14}}}{\rm{C}}$. Out of which, ${}^{{\rm{12}}}{\rm{C}}\;{\rm{and}}\;{}^{{\rm{13}}}{\rm{C}}$ are stable and occurs in a natural proportion of approximately $93:1$. All the three isotopes of carbon have the same number of protons i.e. six while their neutron numbers are different i.e. 6, 7 and 8 respectively.

Complete step by step answer:
having the same atomic number but different mass number. Protons and neutrons are present in the nucleus. The number of neutrons can be determined by knowing the mass number and atomic number. Atomic number for carbon is 6 which is the same for its isotopes.
The atomic number defines the number protons which means for an isotope the number of protons will be the same. The sum of number of protons and number neutrons gives the mass number. Here, the mass number of carbon varies with the isotopes i.e. 12 for ${}^{{\rm{12}}}{\rm{C}}$ and 13 for ${}^{{\rm{13}}}{\rm{C}}$.
${\rm{Mass}}\;{\rm{Number}}={\rm{Number}}\;{\rm{of}}\;{\rm{proton}}+{\rm{Number}}\;{\rm{of}}\;{\rm{neutron}}$ $......\left( 1 \right)$
For ${}^{{\rm{12}}}{\rm{C}}$:
Atomic number of carbon = number of protons = 6
Mass number for ${}^{{\rm{12}}}{\rm{C}}$ = 12
Then, the number of neutrons can be calculated by using equation 1 as:
Number of neutrons $= 12 - 6 = 6$
Now, for ${}^{{\rm{13}}}{\rm{C}}$:
Atomic number of carbon = number of protons = 6
Mass number for ${}^{{\rm{13}}}{\rm{C}}$ = 13
Then, the number of neutrons can be calculated by using equation 1 as:
Number of neutrons $= 13 - 6 = 7$
Therefore, from the above calculations, we can conclude that the nuclei of isotopes will differ in the number of neutrons.

So, the correct answer is Option B.

Note: Carbon isotopes used in many different applications. ${}^{{\rm{13}}}{\rm{C}}$ is used in organic chemistry research, metabolism, studies into molecular structures, air pollution, food labeling and climate change. The ${}^{{\rm{14}}}{\rm{C}}$ which is radioactive used in radiolabeling and radiocarbon dating.