Question

Isotopes of an element contains same number of :

• A. Electrons
• B. Protons
• C. Neutrons
• D. Electrons and protons.

Answer 1

The correct option is D

Electrons and protons.

The explanation for the correct answer

Isotopes of an element contain the same number of electrons and protons.

Option D

• Isotopes are the variations of elements with the same atomic number but different mass numbers.
• Since the atomic number(Z) of an element equals the number of protons or electrons in an atom of an element.

Atomic number (z) = Number of protons = Number of electrons

Example

• Isotopes of Hydrogen are Protium(${}_1{}^1\mathrm{H}$),Deuterium(${}_1{}^2\mathrm{H}$),Tritium(${}_1{}^3\mathrm{H}$).
• All these contain 1 electron or 1 proton.
• Because their atomic number equals 1.

The explanation for the incorrect answers

Option A

• Isotopes are the variations of elements with the same atomic number but different mass numbers.
• Atomic number of an element = Number of electrons = Number of Protons
• Hence Option A is incorrect.

Option B

• Isotopes are the variations of elements with the same atomic number but different mass numbers.
• Atomic number of an element = Number of protons = Number of electrons
• Hence Option B is incorrect.

Option C

• Isotones are the species with the same number of neutrons.
• They have different atomic numbers as well as mass numbers.
• Hence Option C is incorrect.

Example

Sulphur (${}_{16}{}^{36}\mathrm{S}$) and Chlorine(${}_{17}{}^{37}\mathrm{Cl}$) are the examples of isotone.

In ${}_{16}{}^{36}\mathrm{S}$, atomic number = 16

mass number = 36

Neutron number = Mass number - Atomic number = 36-16=20

In ${}_{17}{}^{37}\mathrm{Cl}$, atomic number = 17

mass number = 37

Neutron number = Mass number - Atomic number = 37-17 = 20.

Conclusion: Hence Option D is correct.