Atoms, Elements, Compounds & Mixtures — Condensed Notes

Vocabulary flashcards covering the condensed lecture notes on atoms, subatomic particles, elements, isotopes, compounds, chemical equations, and separation techniques.

Proton

A subatomic particle located in the nucleus with a charge of $+1$ and a relative mass of $1$.

Neutron

A neutral subatomic particle located in the nucleus with a charge of $0$ and a relative mass of $1$.

Electron

A subatomic particle that occupies space around the nucleus, having a charge of $-1$ and a very small relative mass.

Neutral atom

An atom that contains equal numbers of protons and electrons.

Ion

An atom or group of atoms that has gained or lost electrons.

Atomic number

The number of protons found in an atom.

Mass number

The total number of protons plus neutrons in an atom, meaning that $\text{neutrons} = \text{mass number} - \text{atomic number}$.

Element

A substance that contains atoms with the same number of protons, represented by a chemical symbol consisting of one or two letters.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different mass numbers.

Relative atomic mass

The weighted average of an element's isotopes, calculated as $\text{relative atomic mass} = (\text{sum of isotope mass} \times \text{abundance}) \\text{div} (\text{sum of abundances})$.

Compound

A substance containing atoms of two or more elements chemically bonded in fixed proportions, with properties that can differ from those of its constituent elements.

Chemical formula

A notation showing which atoms—and how many—are in a compound; subscripts show atom counts, and a number outside brackets multiplies everything inside (e.g., $Ca(OH)_2$ contains $1$ Ca, $2$ O, and $2$ H atoms).

Mixture

A combination of substances that are not chemically bonded, meaning its parts retain their individual properties and can usually be separated physically.

Balanced equation

A chemical equation in the form of reactants $\rightarrow$ products that has the exact same number of each type of atom on both sides.

Coefficients

Numbers placed in front of chemical formulae that can be altered to balance an equation without changing the formula subscripts (e.g., in $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$).

Filtration

A separation method used to separate an insoluble solid from a liquid.

Residue

The solid left behind on the filter paper during the process of filtration.

Filtrate

The liquid that passes through the filter paper during filtration.

Evaporation

A separation technique that removes the solvent to leave a dissolved solid; used when the solid can withstand heating.

Crystallisation

A technique involving gently concentrating a solution and then cooling it so crystals form, followed by filtering and drying; useful for obtaining purer, larger crystals.

Rock salt separation

A multi-step separation process for salt and sand: dissolve in water $\rightarrow$ filter out sand $\rightarrow$ evaporate or crystallise the salt solution.

Paper chromatography

A method used to separate dissolved substances, such as dyes, by drawing a baseline in pencil, placing the sample above the solvent, allowing the solvent to rise, and then removing and drying the paper.

Chromatogram

The pattern or dried paper result obtained from paper chromatography showing how different substances have traveled different distances.