An electron is a subatomic particle with a negative charge and a very small relative mass of 1/1835 (negligible).

A proton is a subatomic particle with a positive charge and a relative atomic mass of 1.

A neutron is a subatomic particle with no charge and a relative atomic mass of 1.

A nucleus is found in the centre of an atom. It consists of protons and neutrons. It is significantly smaller in size than the atom.

Anything that is smaller than an atom. There are three subatomic particles called electrons, protons and neutrons.

Atomic structure (negligible electron mass)

Combined science

Developing a model for atoms

Atoms, elements and compounds

Modern periodic table and electron configuration

Atomic number and mass number

Isotopes and relative atomic mass

Relative formula mass

Development of the periodic table

In the Structure and Bonding unit, pupils will build on their understanding of atomic structure to explore different types of chemical bonding and how these bonds affect the properties of substances.

In the Atoms, Elements and Compounds unit, pupils learned about the differences between atoms, elements, and compounds, as well as their chemical symbols and formulae.

This unit covers the atomic model, relative atomic mass, isotopes, and the structure of the modern periodic table. It explains how atomic structure influences element positioning, properties, and reactivity. The focus is on identifying trends and using models to develop scientific explanations.

Atomic structure and the periodic table

Model of the atom showing that negative electrons are embedded in a ball of positive charge.

A stream of positive alpha particles fired through a thin piece of gold foil. This lead to an update of the atomic model, from the plum pudding model to nuclear model.

Model of the atom with a small positive charge in the centre surrounded by a cloud of orbiting electrons. The atom is mostly empty space.

An atom is the smallest particle that everything is made up of.

An element is made up of only one type of atom, a list of elements can be found on the periodic table.

A compound is made of two or more different elements chemically bonded together.

The chemical formula of a molecule is a shorthand way of listing the type and number of atoms in a compound.

The chemical composition tells you the different types of atoms in a chemical.

is an energy level outside the nucleus which contains electrons.

of an atom of an element describes how the electrons are arranged in shells.

is a horizontal row on the periodic table, it corresponds to the number of shells of an atom in an element that have electrons in them.

is a column on the periodic table that corresponds to the number of electrons in the outer shell of an atom.

The number of protons in the nucleus of an atom, which determines the element's identity.

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

The mean mass of an atom relative to 1/12th of the mass of a carbon-12 atom.

An atom of an element with the same number of protons, but different mass numbers due to different numbers of neutrons.

A subatomic particle found in the nucleus with a relative mass of 1 and a positive charge (+1).

A subatomic particle found in the nucleus with a relative mass of 1 and no charge.

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

The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element.

RAM is the mean mass of an atom relative to 1/12th the mass of an atom of carbon–12.

(RFM or Mr) is the sum of the relative atomic masses of all the atoms in a chemical formula.

The historical name for atomic mass, i.e. the ratio of the mass of an atom compared to a standard.

The mean mass of an atom compared to 1/12 of the mass of a carbon–12 atom.

A scientist who devised the periodic table of elements.

Atomic structure and the periodic table

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