Year 11 Chemistry: Matter, Atoms, and Radioactivity

Vocabulary practice cards covering the classification of matter, chemical bonding, atomic structure, nuclear decay, and periodic trends based on the lecture notes.

Matter

Anything that has mass and occupies space.

Pure substance

A substance containing only one element or one compound.

Mixture

A physical combination of two or more elements and/or compounds.

Homogeneous mixture

A mixture that is uniform in composition throughout, such as air.

Heterogeneous mixture

A mixture whose composition varies throughout the mixture, such as blood.

Percentage composition

The percentage of the total sample's mass that is made up by a particular component, calculated as $\text{\% composition} = (\frac{\text{mass of component in sample}}{\text{total mass of sample}}) \times 100$.

Organic compound

A compound that contains carbon–hydrogen bonds.

Inorganic substance

Substances that do not contain carbon–hydrogen bonds.

Covalent compound

A compound consisting of atoms of two or more non-metal elements that share electrons.

Ionic bond

The electrostatic attraction between oppositely charged ions, typically formed between a metal cation and a non-metal anion.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Malleable

A property of metals describing the ability to be hammered or shaped without breaking.

Ductile

A property of metals describing the ability to be drawn into wires.

Metalloids

Elements with some metallic and some non-metallic properties.

Alkali metals

Group 1 elements characterized by high reactivity, low melting/boiling points, low density, and softness.

Alkaline earth metals

Group 2 elements that are shiny, silvery in colour, low density, and somewhat reactive.

Noble gases

Group 18 elements that are colourless, odourless, unreactive (inert), and exist as single atoms.

Atomic number ($Z$)

The number of protons in an atom.

Mass number ($A$)

The total number of protons and neutrons in an atom, calculated as $A = p + n$.

Isotopes

Atoms of the same element with the same number of protons but different numbers of neutrons.

Ion

A charged particle formed when the number of protons is not equal to the number of electrons.

Aufbau principle

The rule stating that electrons fill lower-energy orbitals before higher-energy orbitals.

Excited state

The state of an atom where an electron has absorbed energy and moved to a higher energy level.

Emission spectrum

The specific wavelengths or colours of light emitted when electrons move from higher energy levels to lower energy levels.

Absorption spectrum

A continuous spectrum with specific wavelengths missing, produced when electrons absorb specific energies to move to higher levels.

Ionisation energy

The energy required to remove an electron and form an ion.

Electron shielding

The process where inner electrons reduce the attraction between the positively charged nucleus and outer electrons.

First ionisation energy

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous $1+$ ions, denoted as $X(g) \rightarrow X^+(g) + e^-$.

Relative atomic mass ($Ar$)

The average mass of the relative isotopic masses of an element, calculated using $Ar = \frac{[M_1(\%_1) + M_2(\%_2) + \dots]}{100}$.

Alpha particle ($\alpha$)

A helium nucleus containing $2$ protons and $2$ neutrons, having a mass of $4$ and a charge of $+2$.

Beta particle ($\beta$)

An electron emitted from the nucleus when a neutron decays into a proton and an electron.

Gamma radiation ($\gamma$)

High-energy electromagnetic radiation with high frequency and short wavelength; it has no mass and is highly penetrating.

Half-life

The average time required for the number of radioactive nuclei in a sample to decrease to half its original amount.

Radioactive tracer

A substance, such as technetium-99m, used in medicine to trace body functions and diagnose diseases like tumours or clogged arteries.

Periodicity

The recurring trends observed in elemental properties.

Core charge

The attractive force experienced by valence electrons due to the nucleus, calculated as $\text{Core charge} = \text{number of protons} - \text{inner-shell electrons}$.

Electronegativity

A measure of an atom's tendency to attract bonding electrons.