atoms

Atom

The basic unit of matter that defines the structure of an element.

Nucleus

The dense central core of an atom, surrounded by negatively charged electrons.

Protons

Positively charged particles found within the nucleus of an atom.

Neutrons

Uncharged (neutral) particles found within the nucleus of an atom.

Electrons

Negatively charged particles that orbit the nucleus in energy levels.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom, defining the chemical identity of an element.

Mass Number ($A$)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

Shell Capacity

The maximum number of electrons that can occupy a given energy level $n$, given by the formula $2n^2$.

Relative Atomic Mass (A\text{_r})

The weighted average mass of an atom of an element relative to $\frac{1}{12}\text{th}$ of the mass of an atom of Carbon-12.