Which of the following pairs is/are correctly matched?
1. Isotopes : Atoms with same atomic number but different atomic mass.
2. Isobars : Atoms with same number of neutrons but different atomic number.
3. Isotones : Atoms with same mass number but different atomic number.
Select the correct answer using the codes given below :

Options

A. 1, 2 and 3
B. 1 only
C. 1 and 2 only
D. 2 only

Answer

B

Explanation

Isotopes are variants of a particular chemical element: while all isotopes of a given element share the same number of protons and electrons, each isotope differs from the others in its number of neutrons. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively.