IEB Chemistry Definitions

Mass number (A)

the total number of protons and neutrons in an atom

Atomic number (Z)

the number of protons in an atom

Isotope

Atoms of the same element with different mass numbers / atoms of the same element with the same atomic number but different mass numbers

Ion

A species in which there is a surplus or lack of electrons

First ionisation energy

The amount of energy required to remove the outer most electron from a gaseous atom in its ground sate

Ionic bond

A transfer of electrons and subsequent electrostatic attraction

Covalent bond

The sharing of at least one pair of electrons between two atoms

Electronegativity

a measure of the tendency of an atom to attract a bonding pair of electrons

non polar covalent bond

An equal sharing of electrons

polar covalent bond

unequal sharing of electrons leading to a dipole forming (as a result of electronegativity difference)

Intermolecular forces

The weak force of attraction between molecules, ions or atoms in noble gases

intramolecular bonds

A bond which occurs between atoms within a molecule

Giant covalent substance

A substance which contains a large network of covalent bonds

Allotrope

different structural forms of the same element

Metallic bond

A bond between a positive kernel and a sea of delocalised electrons

Mole

The amount of any substance that contains the same number of elementary particles as 12g of Carbon-12

Relative atomic mass (Aᵣ)

The average mass of one atom of an element relative to Carbon-12, which has mass exactly 12

Relative molecular mass (Mᵣ)

The average mass of one molecule relative to Carbon-12, which has mass exactly 12

Law of conservation of matter

Matter cannot be created or destroyed, only transferred from one place to another

Molar mass (M)

The mass in grams of one mole of that substance

Empirical formula

The formula that shows the simplest ratio of elements in the compound

Molecular formula

The formula that shows the actual ratio of elements in a compound

Standard solution

A solution of which the concentration is know exactly, and is unlikely to change for a period of time

Solution

A homogenous mixture of solute and solvent

Solute

The substance that is dissolved in the solution

Solvent

the substance in which another substance is dissolved, forming a solution

Concentration

The amount of solute per unit volume of solution

Atomic mass unit (amu)

one twelfth the mass of a carbon-12 atom

grams per mole (g/mol)

unit of molar mass

Molar volume of gas (Vₘ)

22.4 dm³

1dm³ = ____ m³ = ____ cm³ = ____mm³

0,001 AND 1000 AND 1 000 000