Structure of The Atom Notes

• Isotopes are atoms of the same element having the same atomic number but different mass numbers.
• Isotopes of an element have the same atomic number because they contain the same number of protons (and electrons) but different number of neutrons in their nuclei.

For example:

• All the isotopes of an element contain the same number of protons and electrons, therefore, the chemical properties of all the isotopes of an element are identical (or same).

The Physical Properties of the Isotopes of an Element are Different:

• Due to the presence of different number of neutrons, (as neutron is the heaviest particle among proton, electron and neutron) the masses of all the isotopes of an element are slightly different.
• Since the mass of the isotopes of an element are slightly different, the physical properties of the isotopes of an element are slightly different.

Radioactive isotopes:

• Isobars are the atoms of different elements having different atomic numbers but the same mass number (or same atomic mass).
• Isobars have different number of protons in their nuclei but the total number of nucleons (protons + neutrons) in them is the same.

argon  and calcium .