Isotopes

Key definition

• Isotopes are different atoms of the same element that have the same number of protons but different number of neutrons.
  • Isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration.

Writing symbols for atoms and ions

Atoms

• For atoms, the top number is represented as the nucleon number. The nucleon number is calculated as the number of protons and neutrons.
• The bottom number is represented as the proton number (also called the atomic number, and the electron number).

Ions

• For ions, the same concept for atoms is applied here, but the valid charge is written at the top right of the element.

Relative atomic mass

• In order to calculate the relative atomic mass of an element, you need these values:
  • the relative masses
  • the relative abundances

Formula

$$A_r=\frac{({\text{mass}}_1\times {\text{abundance}}_1)+({\text{mass}}_2\times {\text{abundance}}_2)}{100}$$