- Atoms always have as many electrons as protons.
- Atoms usually have as many neutrons as protons.
- The number of protons in an atom is fixed. Adding a proton makes a
new kind of atom. Adding a neutron makes an isotope of that atom ( a
heavier version of that atom ).
- Therefore, isotopes are atoms of the same element with different number of
neutrons. They have the same number of protons (ie. proton number) but
different atomic mass.
Isotopes of Hydrogen
Hydrogen has three isotopes, with atomic mass 1, 2 and 3. They all
contain the same number of protons and electrons but differ in the number of
Isotopes of Carbon
- Isotopes of the same element have the same chemical properties and form
compounds with the same formula.
- There are some differences in physical properties eg. boiling point.
- There are two types of isotopes : radioactive and non-radioactive.