Atomic Structure - Isotopes

Isotopes are atoms of the same element that contain the same number of protons but different numbers of neutrons. This means they have the same atomic number ($Z$) but different mass numbers ($A$).

In nuclear notation, an isotope is represented as $^{A}_{Z}X$, where $X$ is the chemical symbol, $A$ is the mass number (protons + neutrons), and $Z$ is the atomic number (protons).

Isotopes of the same element have identical chemical properties because they have the same number of electrons and the same electronic configuration (e.g., $2, 8, 1$ for Sodium isotopes).

Physical properties, such as density, melting point, and boiling point, differ slightly between isotopes because these properties are influenced by the mass of the nucleus.

The Relative Atomic Mass ($A_r$) of an element is the weighted average of the masses of its naturally occurring isotopes relative to $\frac{1}{12}$ of the mass of a $^{12}C$ atom.