Question

Explain isotopes and isobars with examples.

Answer 1

Hint: Hydrogen atoms have 3 isotopes, chlorine has 2 isotopes. Isotopes are different by the mass number. There are 3 elements in the periodic table which have mass number 40 and these are isobars.

Complete step by step answer:
An element has an atomic and mass number. The atomic number of an element is represented with Z and the mass number is represented by A.
The atomic number tells the total number of protons in the nucleus or the total number of electrons present in the neutral atom.
 The mass number tells the sum of the number of protons and the number of neutrons present in the atom.
The mass number is written superscript to the symbol of the atom and the atomic number is written subscript to the symbol of the atom.
In some cases, atoms of the same element are found to have the same number of protons but a different number of neutrons. So, it can be noted that such atoms have the same atomic number but a different mass number. These atoms are called isotopes. For example, the hydrogen atom has three isotopes having mass numbers 1, 2, and 3 respectively and each having an atomic number equal to 1. They are $_{1}^{1}H,_{1}^{2}H\text{ and }_{1}^{3}H$.
In some cases, different atoms have the same mass number but different atomic numbers. These are called isobars. For example, some atoms of calcium, argon, and potassium have mass number 40, but the atomic number of argon is 18, the atomic number of potassium is 19, and the atomic number of calcium is 20. They are $_{18}^{40}Ar,_{19}^{40}\text{K and }_{20}^{40}Ca$.

Note: There are some other terms also like isotones, that says the atoms having the same number of neutrons, and isoelectronic, that says the atoms having the same number of electrons.