Chemistry: Properties of Matter - Atomic Structure (Protons, Neutrons, Electrons)

The atom is the basic building block of matter, consisting of a central nucleus and surrounding electron shells.

The nucleus contains protons ($p^+$) which have a positive charge of $+1$ and a relative mass of $1$, and neutrons ($n^0$) which have a neutral charge and a relative mass of $1$.

Electrons ($e^-$) orbit the nucleus in specific energy levels or shells; they have a negative charge of $-1$ and a negligible mass (approximately $\frac{1}{1840}$ of a proton).

The Atomic Number ($Z$) is the number of protons in the nucleus and defines the identity of the element.

The Mass Number ($A$) is the total number of protons and neutrons in the nucleus.

In a neutral atom, the number of protons is equal to the number of electrons, resulting in a net charge of $0$.

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, resulting in different mass numbers (e.g., $^{12}_{6}C$ and $^{14}_{6}C$).

Standard nuclide notation is written as $^{A}_{Z}X$, where $X$ is the chemical symbol, $A$ is the mass number, and $Z$ is the atomic number.