Question

A nucleus of element X is represented as ${}_{26}^{56}X$. Which is an isotope of element X?
A. ${}_{56}^{26}X$
B. ${}_{26}^{54}X$
C. ${}_{28}^{54}X$
D. ${}_{28}^{54}X$

Answer 1

Hint: Isotope is one or more chemical species with the same atomic number and different mass number. Isotopes of certain elements have the similar number of protons but different numbers of neutrons in each atom.

Complete step by step answer:
Isotopes are species or atoms or elements of a particular chemical form which differ in neutron number, and consequently differ in nucleon number. This kind of chemical species are known as isotopes. Isotopes of certain elements have the similar number of protons but different numbers of neutrons in each atom. Since isotopes have different numbers of nucleons they have different mass numbers. Isotopes are formed during any nuclear processes generally. As the nucleon number is not stable, their nucleus will not be stable enough. This will lead to the decay of the nucleus which will cause radioactivity in some isotopes.
Therefore the answer for this question is option (b).

Note:
Isotopes are having different mass numbers. Atomic number is different in case of isobars. Don’t get messed up with these two. Isotopes are having similar chemical characteristics like ionisation energy. This is because of the similar number of electrons in both the species. However the physical properties like melting point, boiling point, density are different as they depend on the mass number of the species. Example for an isotope is chlorine 35.5 and 37. Every chemical element is having one or more isotopes generally. Overall there are 3800 radioisotopes discovered. In which around 200 isotopes have been used on a regular basis. Almost all isotopes are being artificially manufactured. The common method is neutron activation in nuclear reactors.