Science Revision flashcards

Atom

The smallest part of an element that still has its properties

Molecule

Two or more atoms chemically bonded together

Compound

A substance made of two or more different atoms chemically combined

Pure substance

A material made of only one type of particle

Mixture

A combination of substances not chemically bonded

Group

A vertical column on the periodic table

Period

A horizontal row on the periodic table

Metals

Elements that are shiny, conduct heat/electricity, and are on the left side of the table

Non‑metals

Elements that are dull, brittle, poor conductors, and on the right side

Metalloids

Elements with properties of both metals and non‑metals

Electrons

Negatively charged particles in shells around the nucleus

Protons

Positively charged particles in the nucleus

Neutrons

Neutral particles in the nucleus

Orbit shells

The energy levels where electrons are found

Nucleus

The centre of the atom containing protons and neutrons

Ionic bond

A bond between a metal and a non‑metal where electrons are transferred

Covalent bond

A bond between two non‑metals where electrons are shared

Mass number

The total number of protons and neutrons

Atomic number

The number of protons in an atom

Number of protons

Equal to the atomic number

Number of electrons

Equal to the number of protons in a neutral atom

Number of neutrons

Mass number minus atomic number

Electron configuration

The arrangement of electrons in shells around the nucleus

How to write electron configuration

Fill shells in order: 2, 8, 8, 2

Ion

A charged atom that has gained or lost electrons

Group 1 charge

+1

Group 2 charge

+2

Group 17 charge

-1

Group 18 charge

0 (stable)

Electron configuration of an ion

Draw with a full outer shell after electrons are gained or lost

Why symbols are used on the periodic table

To represent elements clearly and universally

Monatomic

Single atoms not bonded to others

Molecules

Two or more atoms bonded together

Diatomic

Molecules made of two atoms

Polyatomic

Molecules made of many atoms

Lattice

A large, repeating 3D structure of atoms or ions

Chemical formula

Shows which elements and how many atoms are in a compound

Counting atoms in a compound

Use subscripts to determine the number of each atom

Difference between compounds and mixtures

Compounds are chemically bonded; mixtures are not

Example of a compound

Water (H₂O)

Example of a mixture

Air or saltwater

Homogeneous mixture

A mixture that looks the same throughout

Heterogeneous mixture

A mixture where different parts are visible

Why Group 18 is monatomic

They have full valence shells and are already stable

Why many elements are diatomic

They bond to achieve a full outer shell following the octet rule

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