Question

What are isotopes? Give an example as well.

Answer 1

Elements or atoms that have the same number of electrons but different number of neutrons in their nuclei are known as isotopes. Hydrogen has three isotopes. They are Hydrogen, Deuterium and Tritium. Isotopes also differ in masses.

Complete answer: An atom is represented by writing its atomic number and mass number with its symbol i.e. ${}_Z^AX$ where X is the symbol of element, Z is the atomic number and A is the mass number.The atomic number represents the number of electrons present in the element.The mass number represents the total number of protons and neutrons present in it.In isotopes, the total number of electrons are equal but the total number of neutrons present differ.This means that they have the same Z value but different A value. These values usually differ by one or two in numbers.For example: The three isotopes of hydrogen are Hydrogen, Deuterium and Tritium.
The element hydrogen is written as ${}_1^1H$
The element deuterium is written as ${}_1^2D$
The element tritium is written as ${}_1^3T$
All these three elements have one electron in them but differ in the number of neutrons present in them. Hence they are known as isotopesThe element having the highest number of neutrons i.e. tritium is the heaviest of them all and the element having the least number of neutrons i.e. hydrogen is the lightest.

Note: Similar to isotopes, there also exist isobars, isotones etc. Isobars are elements that have the same atomic weight. Atoms or elements that have the same number of neutrons but different numbers of protons are known as isotones.