Question

The atoms of different elements with the same mass number, but different atomic numbers are called ________.

Answer 1

• Atomic number(Z)- The total number of protons in the nucleus of an atom gives us the atomic number of that atom.
• Mass number(A)- The number of protons and neutrons combine to give us the mass number of an atom.
• Isobars- The atoms of different elements with the same mass number, but different atomic numbers are called isobars.

Example-

• ${}_{20}{}^{40}\mathrm{Ca}$ and ${}_{18}{}^{40}\mathrm{Ar}$ are isobars.
• Calcium atom has 20 protons and 20 neutrons which combines to have 40 as mass number.
• Argon atom has 18 protons and 28 neutrons and it also has a mass number of 40.
• Since, these two examples have the same mass number, they are isobars.

The atoms of different elements with the same mass number, but different atomic numbers are called isobars.