Atomic Structure

Nucleons

Sub-atomic particles that exist in the nucleus of atoms (protons and neutrons).

Strong nuclear force

Forces that hold together protons and neutrons in the nucleus.

Electrostatic forces

Forces of attraction existing between any positive and negative particles.

Isotopes

Atoms of the same element with different numbers of neutrons.

Relative atomic mass (Ar)

Weighted average mass of an atom compared to one twelfth of a carbon-12 atom.

Relative isotopic mass

Mass of an atom of an isotope compared to one twelfth of a carbon-12 atom.

Atomic number (Z)

The number of protons in the nucleus of an atom.

Mass number (A)

The total number of protons and neutrons in the nucleus.

Species (chemistry)

A substance composed of chemically identical entities.

Main shell (quantum shell)

Made up of sub-shells containing orbitals where electrons are found.

Orbital

A region of space in an atom containing up to two electrons with opposite spins.

Sub-shell

One or more orbitals in the same shell which have the same energy levels.

s-block element

An element with its highest energy electron in an s orbital.

p-block element

An element with its highest energy electron in a p orbital.

d-block element

An element with its highest energy electron in a d orbital.

Transition metals

Elements which form at least one stable ion with partially filled d orbitals.

First ionisation energy

Energy required to remove one mole of electrons from one mole of atoms in the gaseous state.

Second ionisation energy

Energy required to remove one mole of electrons from one mole of 1+ ions in the gaseous state.

Successive ionisation energy

Energy required to remove the electrons one after the other.

Periodicity

A regularly repeating pattern of atomic, physical, and chemical properties with increasing atomic number.