Chemistry Unit 1

Semester 1 2026

Atom

The basic building block of matter. It is made up of subatomic particles , protons, neutrons and electrons.

Atomic Number

The number of protons in the nucleus of an atom

Chemical Property

A property which can only be measured by reacting the substance chemically

Chemical Symbol

A symbolic representation of an element, usually one or two letters.

Compound

A pure substance made up of different types of atoms combined in a fixed ratio.

Diatomic

A molecule formed from two atoms only

Electron

A negatively charged, subatomic particle that occupies the region around the nucleus of an atom.

Electrostatic attraction

The force of attraction between a positively charged particle and a negatively charged particle.

Element

A substance made up of atoms with the same atomic number.

Ions

An atom or group of atoms with a positive or negative charge

Isotope

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.

Mass number

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

Monoatomic

Exists as a single atom of any element.

Neutron

An uncharged subatomic particle found in the nucleus of an atom.

Nucleon

A particle that makes up the nucleus of an atom. Protons and neutrons

Nucleus

The positively charged core at the center of an atom, consisting of protons and neutrons

Nuclide notation

A way of representing an atom using the element symbol, atomic number, and mass number.

Physical Property

A property which can be measured without changing the substance into another substance.

Proton

Positively charged subatomic particles bound to neutrons in the nucleus of an atom.

Radioactive

Spontaneously undergoing nuclear decay to produce radiation such as beta particles alpha particles, gamma rays.

Relative atomic mass

The mass of an atom compound or molecule relative to the mass of an atom of C-12

Subatomic particle

A particle that makes up an atom, protons, neutrons and electrons

Bohr model

A theory of the atom proposed by Niel Bohr whihc states that electrons in an atom occupy fixed circular orbits that correspond to specific energy levels.

Electron shells

In a shell model of an atom, an electron shell is the fixed energy level that correpsond to a circular obrit level of the electrons

Electronic configuration

is a means of representing the number of electrons in each shell

Emission spectra

A spectrum produced when an element is excited by heat or radiation, It appears as distinct lines characteristic of the element.

Energy State

One of the diffeent level swhich are occupied by leectrons.

Excited state

Describes an atom in which electrons occupy a higher electron shell than teh loer energy levels possible.

Ground State

An atom in which the electrons occupy the lowest possible energy levels

Valence electron

An electron found in the outermost shell of an atom.

Valence shell

The highest energy shell of an atom that contains electrons, outermost shell

Condensed electron configuration

A shortened way of writing an electron configuration by using a noble gas before the element.

Orbital

An orbital is a component of s ubshell It is a region of space in which electrons move.

Quantum mechanics

A branch of science that describes the behaviour of extremely small particles such as electrons.

Subshells

Component of a shell made up of orbitals, each subshell can be regarded as an energy level that electrons can occupy.

Actinoids

They are located at the bottom of a periodic table, in period 7 of the f block

Alkali metals

A group 1 metal

Alkaline earth metals

Group 2 elements, they readily form +2 cations

Atomic radius

The distance from teh nucleus to the outermost electron, increase down a group, decrease across a period.

Block

Sections of the periodic table they determine th valence subshell.

Critical elements

Elements which are heavily relied upon by industry and scoiety which face some form of supply uncertaonty.

Groups

A vertical coluumn down a periodic table

Halogens

A group 17 element

Lanthanoids

found in period 6 of the f block

Metallic character

Is teh tendency for atoms to lose electrons and form cation, positibe ions,

Metalloids

An element which displays both metallic and non-metalliuc properties

Noble gases

An unreactive gaseous elemnt in group 17 of the periodic table, aprt from helium they have 8 electrons in their valence shell

Periods

A horizontal row of elements in teh periodic table, a new row correpsonds to a new shell.

Transition metals

An element in group 3-12 of the periodic table

Effective nuclear charge/core charge

The net positive charge experienced by an electron in an outer shell of an atom. It indicates teh attractive forece felt towards the nucleus by the valence electrons.

Electronegativity

The ability of an atom to attract electrons iun a acovalent bond towards itself.

Electrostatic force of attraction

The forec of attraction between a positively charge particle and a negatively charge dparticle

First ionization energy

The minimum amount of energy required to remove one electron from at atom WHILE IN THE GASEOUS STATE

Alloy

A substance forned when other materials are mixed with a metal

Cation

A positivelu chareg iion

Conductivity

Is teh ability of an atopm to conduct heat or electricuity.

Delocalized electron

An electron that is not restricted to teh region between two atoms.

Density

A measure of teh amount of mass per unit volume.

Ductility

An ability of a metal to be able to be drawn into a wire or stretched

Lattice

A regulare arrangement of large number of atoms, ions, or molecules

Lustre

Is the ability of an element to relfect light from its surface givong it a shiny appearance

Malleability

Th ability toi be able to be bent or beaten into sheets

Tensile strength (hardness)

The maximum resistance of a material to force which is pulling it apart befroe breaking.

Inert

Not chemically reactive (noble gases)

Reactivity

The ease with which a chemical can undergo reactions

Circular economy

An economy based on a model of production which aims to design out waste and pollution, keep products and materials in use adn regenrate natural systems.

Electrolysis

The production of a reaction by teh passage of electrical energy.

Ferrous

A material containing iron

Linear Economy

An economy in which raw materials are used to produce a proudtct and after the product is used it is thrown away.

Molten

Matgerials that are normally found as solid but ar eliquid

Non-ferrous

a metal other than iron or steel

Smelting

A process of applying heat to ore to extract a metal

Anions

A negativelky charged atom

Brittle

Shatters when given a sharp tap

Chemical Formula

A representation of a substance using symbols for its constituent elemnents, it shows the ratio of atoms presnt in teh substance,

Crystal lattice

Th esymmetrical three dimensional arrangement of atoms or ions within a crystal

Dissolve

To incorporate a solid gas into liquid so as to forma solution

Electrolyte

A solution or molten substaance that consudcts electricityby means if movement f ions

Ion - dipole attraction

is the electrostatic force of attraction between an ion and a polar molecule.

Ionic bond

Ionic compound

Solubility

Electron transfer diagram

Polyatomic ions

Empirical formula

Aqueous

Dissolution

Double replacement reaction

Insoluble

Ionic equation

Precipitate

Precipitation reaction

Solubility

Soluble

Spectator ion

Bond length

Bond strength

Covalent bond

Electronegativity

Intramolecular bonds