Chemistry 1/2 Glossary

atom

Smallest unit of matter

element

A pure substance made of only one kind of atom

compound

Two or more atoms of different elements bonded together

atomic number

Number of protons

mass number

Number of protons and neutrons

isotope

Atoms that have the same number of protons but different number of neutrons

ion

Atoms that have lost or gained one or more electrons

molecule

Two or more atoms held together by covalent bonds

orbitals

Regions with the highest probability of finding electrons

Aufban principle

States that subshells are filled by electrons from lowest to highest energy level

atomic radius

One-half the distance of an atom, starting from the middle of the nucleus

core charge

A measure of the attractive force felt by the valence shell electrons towards the nucleus

electronegativity

The ability of an element to attract shared electrons towards itself

first ionisation energy

The energy required to remove the first valence electron from an atom

metallic character

Degree to which an element is shiny and conducts electricity. Depends on how easily electrons are lost

reactivity

The tendency of an atom to lose or gain electrons

linear economy

When natural resources follow a "take-make-dispose" model wherein waste is created and not reused

circular economy

When natural resources are used and reused to be incorporated into new products

alloy

Mixture of elements with base metals

covalent bonding

Intramolecular bond formed between non-metallic atoms through shared valence electrons.

intramolecular bonding

Bonding between atoms in a molecule

intermolecular bonding

Bonding between molecules

dipole

Polar molecule

dispersion forces

Present between both polar and non-polar molecules due to instantaneous dipoles

dipole-dipole attraction

Present between adjacent permanent dipoles

hydrogen bonding

Present between a H bonded to a F, O or N on one molecule, and an adjacent F, O or N a second molecule

FONCl or FOClN

Decreasing order of electronegativity

melting point

The temperature at which a substance changes its state from a solid to a liquid

boiling point

The temperature at which a substance boils and changes its state from a liquid to a gas

hardness

Resistance to deformation when subjected to pressure

isomers

Molecules with the same molecular formula (e.g. pentane C5H12 and dimethylpropane, C5H12)

allotrope

One of the different physical forms of an element due to different structural arrangements of atoms

diamond structure

Bonded in a 3D covalent network lattice

properties of diamond

high melting point, very hard, brittle, does not conduct electricity, insoluble

graphite structure

Covalent layer lattice with layers of 2D carbon lattices held by weak dispersion forces. Lattice has delocalised electrons that are free to move within

properties of graphite

high melting point, high thermal conductivity, soft and slippery, conducts electricity

crystal lattice (ionic)

symmetrical, three-dimensional arrangement of ions

molten

a pure substance that has been liquefied by heat

coordination number

the number of atoms, molecules or ions bonded to a chemical species

misconception: there are covalent bonds in a crystal lattice

there are no covalent bonds in a crystal lattice, as electrons are not being shared between atoms, they are being transferred from a metal atom to a non-metal atom

conductivity in ionic compounds

for a substance or material to be electrically conductive, they need to have mobile charged particles. This can only happen when ionic compounds are in an aqueous or molten state, as when they are in a crystal lattice (solid state), the charged particles are fixed. Cations are attracted to the - electrode, while anions the + electrode

brittleness in ionic compounds

when a strong force is exerted on an ionic compounds, repulsive forces between like-charged particles will shatter and break the lattice