AQA GCSE Chemistry Topic 1: Atomic Structure and the Periodic Table

Vocabulary flashcards covering atoms, elements, compounds, mixtures, subatomic particles, isotopes, RAM, electronic structure, and key experiments.

Atom

The smallest unit of an element that can exist; makes up all substances and contains a nucleus surrounded by electrons.

Element

A pure substance made of only one type of atom.

Chemical symbol

A one- or two-letter shorthand for an element, e.g., Na for sodium.

Compound

A substance formed from two or more elements in fixed proportions; properties differ from the elements; formed by chemical reactions; can be represented by chemical formulae.

Formula

A notation showing the elements and their numbers in a compound, e.g., HCl.

Mixture

Two or more substances physically combined; not chemically bonded; each keeps its properties; separable by physical methods.

Filtration

Physical separation method used to separate insoluble solids from liquids.

Simple distillation

Separation method based on different boiling points to separate a liquid from a solution.

Fractional distillation

Separation method for liquids with different boiling points using a fractionating column.

Chromatography

Separation method based on different movement rates of substances through a stationary phase.

Plum pudding model

Early atomic model: a ball of positive charge with embedded electrons.

Rutherford alpha scattering experiment

Experiment showing most alpha particles passed through gold foil but some were deflected, indicating a small, dense, positively charged nucleus.

Nucleus

The centre of an atom containing protons and neutrons; contains most of the atom’s mass and is positively charged.

Proton

+1 charge; located in the nucleus; mass roughly 1 atomic unit.

Neutron

0 charge; located in the nucleus; mass roughly 1 atomic unit.

Electron

-1 charge; orbits the nucleus in shells; very small mass.

Atomic number

The number of protons in an atom; determines the element; in a neutral atom, also equals the number of electrons.

What is an Isotope

Atoms of the same element with different numbers of neutrons; have different mass numbers.

What is Relative atomic mass

An average mass of an element’s atoms, weighted by the abundances of its isotopes.

What is Electronic structure

Arrangement of electrons in shells around the nucleus; indicates how many electrons are in each shell (e.g., Na = 2, 8, 1).

Who is Bohr

Scientist who proposed that electrons orbit the nucleus at specific distances in energy levels.

Who is Chadwick

Scientist who provided evidence for the existence of neutrons in the nucleus.