Unit 1 Definitions

Question 0

Relative isotopic mass

Answer 0

The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of Carbon-12.

Question 1

Isotopes

Answer 1

Elements which have gained or lost neutrons, but have the same number of protons.

Question 2

Relative atomic mass

Answer 2

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of Carbon-12. NO UNITS!

Question 3

Relative molecular mass

Answer 3

The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of Carbon-12.

Question 4

Relative formula mass

Answer 4

The weighted mean mass of a formula unit compared with one-twelfth or the mass of an atom of Carbon-12.

Question 5

First ionisation energy

Answer 5

The energy required to remove one electron from every atom or a mole of atoms in the gaseous state.

Question 6

Oxidising agent

Answer 6

Makes something else oxidise

Question 7

Reducing agent

Answer 7

Makes something else reduce

Question 8

Acid

Answer 8

An acid released H+ ions in aqueous solution. An acid is a proton donor.

Question 9

Base

Answer 9

Bases are proton acceptors.

Question 10

Alkali

Answer 10

An alkali is a soluble base that releases OH- ions in water.

Question 11

Salt

Answer 11

Salts are ionic compounds formed when the H+ ions in acids are replaced by metal ions or ammonium ions.

Question 12

Amount of substance

Answer 12

The quantity whose unit is the mole.

Question 13

Mole

Answer 13

The amount of any substance containing as many particles as there are Carbon atoms in exactly 12g of the carbon -12 isotope.

Question 14

Avogadro Constant

Answer 14

The number of atoms per mole of Carbon-12 isotope, 6.02x10^23 mole^-1

Question 15

Molar mass

Answer 15

The mass per mole of a substance in g/mol

Question 16

Empirical formula

Answer 16

The simplest whole number ratio if the atoms of each element in a compound.

Question 17

Molecular formula

Answer 17

The actual number of atoms of each element in a molecule.

Question 18

Anhydrous

Answer 18

A substance containing no water molecules.

Question 19

Hydrated

Answer 19

Crystalline and containing water molecules.

Question 20

Water of crystallisation

Answer 20

Water molecules that form an essential part of the crystalline structure of a compound.

Question 21

Molar gas volume

Answer 21

The volume occupied by one mole of a gas with units dm^3/mol^-1

At rtp, one mole of gas occupies 24dm^3.

Question 22

Ionic bonding

Answer 22

The electrostatic attraction between oppositely charged ions.

Question 23

Covalent bond

Answer 23

A bond formed by a shared pair of electrons.

Question 24

Dative covalent bond

Answer 24

A shared pair of electrons which had been provided by one of the bonding atoms only.

Question 25

Metallic bonding

Answer 25

The electrostatic attraction between positive metal ions and delocalised electrons.

Question 26

Van Der Waals’ forces

Answer 26

Attractive intermolecular forces that act between non-polar molecules.

Question 27

Electronegativity

Answer 27

The ability of an atom to attract the bonding electrons in a covalent bond.

Question 28

Permanent dipole

Answer 28

A small charge difference across a bond that results from a difference in electronegativities of the bonded atoms.

Question 29

Polar covalent bond

Answer 29

A bond with a permanent dipole

Question 30

Polar molecule

Answer 30

A molecule with an overall dipole

Question 31

Hydrogen bond

Answer 31

The attraction between a hydrogen atom bonded to a nitrogen, fluorine or oxygen atom and a lone pair on another nitrogen, oxygen or fluorine atom.