Question

Isotopes are:
A. Atoms of the same element, having different atomic numbers but same mass numbers.
B. Atoms of same elements, having the same atomic number but different mass numbers.
C. Atoms of different elements with different atomic numbers, which have the same mass number.
D. Atoms of different elements with the same atomic numbers, which have different mass numbers.

Answer 1

Hint: We know that Atoms and elements are made of proton, neutron and electron. The nucleus is made of protons and neutrons, and the electrons surround the nucleus. In isotopes, there is some variation in the composition of nucleus.

Complete step by step answer:
Isotopes of an element possess the similar number of protons and hence same number of protons and hence have the same number of electrons since the electrons are responsible for chemical properties, isotopes of an element, show similar chemical properties.
Let us consider an example of isotopes, for hydrogen, there are three type of isotopes, which are protium, \[\left( {H_1^1} \right)\] deuterium\[\left( {H_1^2} \right)\], and tritium. \[\left( {H_1^3} \right)\] They have the same atomic number but different atomic masses. The number of neutrons can be calculated by calculating the difference between the atomic number mass and atomic number. We can say that the isotopes of hydrogen have varying numbers of neutrons. For protium, the number of neutrons is one, and for tritium, the number of neutrons is two. And in tritium the number of neutrons is 3.
So “isotopes are atoms with the same number of protons but have a different number of neutrons”. In other words, they are atoms with the same atomic number but with a different mass.

Hence, the correct option is B.

Note: Isotopes have various medical, security and research uses. The Americium 241 isotope is used in many smoke detectors for homes and businesses, to measure levels of toxic lead in dried paint samples.