As Chemistry Ocr 2011 Topic 1 Keywords

Front 1

Acid

Back 1

A species that is a proton donor.

Front 2

Alkali

Back 2

A type of base that dissolves in water forming hydroxide ions, OH-(aq) ions.

Front 3

Amount of Substance

Back 3

The quantity whose unit is the moles. Chemists use 'amount of substance' as a means of counting atoms.

Front 4

Anhydrous

Back 4

A substance containing no water molecules.

Front 5

Anion

Back 5

A negatively charged ion.

Front 6

Atom economy

Back 6

(Molecular mass of desired product / Sum of molecular masses of all products) x 100.

Front 7

Atomic Orbital

Back 7

A region within an atom that can hold up to two electrons, with opposite spins.

Front 8

Atomic Number/Proton Number

Back 8

The number of protons within the nucleus of the atom.

Front 9

Avogadro's Constant

Back 9

The number of atoms per mole of the carbon-12 isotope (6.02 x 10^23 mol-1).

Front 10

Base

Back 10

A species that is a proton acceptor.

Front 11

Cation

Back 11

A positively charged ion.

Front 12

Compound

Back 12

A substance formed from two or more chemically bonded elements in a fixed ration, usually shown by a chemical formula.

Front 13

Concentration

Back 13

The amount of solute, in mol, per 1dm^3 (1000cm^3) of solution.

Front 14

Covalent Bond

Back 14

A bond formed by a shared pair of electrons.

Front 15

Dative Covalent Bond

Back 15

A shared pair of electrons which has been provided by one of the bonding atoms only; also called a Co-ordinate bond.

Front 16

Dehydration

Back 16

An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.

Front 17

Delocalised Electrons

Back 17

Electrons that are shared between more than two atoms.

Front 18

Displacement Reaction

Back 18

A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ions.

Front 19

Disproportionation

Back 19

The oxidation and reduction of the same element in a redox reaction.

Front 20

Electron Configuration

Back 20

The arrangement of electrons in an atom.

Front 21

Electronegativity

Back 21

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

Front 22

Electron Shielding

Back 22

The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons.

Front 23

Empirical Formula

Back 23

The simplest whole-number ratio of each element present in a compound.

Front 24

Giant Covalent Lattice

Back 24

A three-dimensional structure of atoms, bonded together by strong covalent bonds.

Front 25

Giant Ionic Lattice

Back 25

A three-dimensional structure of oppositely charged ions, bonded together by strong ionic bonds.

Front 26

Giant Metallic Lattice

Back 26

A three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.

Front 27

Hydrated

Back 27

Crystalline and containing water molecules.

Front 28

Hydrocarbon

Back 28

An organic compound of Hydrogen and Carbon only.

Front 29

Hydrogen Bond

Back 29

A strong dipole-dipole attraction between an electron-deficient hydrogen atom (O-H+ of N-H+) on one molecule and a lone pair of electrons on a highly electro negative atom (H-O- or H-N-) on a different molecule.

Front 30

Hydrolysis

Back 30

A reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds.

Front 31

Intermolecular Force

Back 31

An attractive force between neighbouring molecules. Intermolecular forces can be van der Waals' forces (including dipole-dipole forces), permanent dipole-diploe forces or hydrogen bonds.

Front 32

Ion

Back 32

A positively or negatively charged atom or (covalently bonded) group of atoms (a molecular ion).

Front 33

Ionic Bond

Back 33

Electrostatic attraction between oppositely charged ions.

Front 34

First Ionisation Energy

Back 34

The energy required to remove one election from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Front 35

Second Ionisation Energy

Back 35

The energy required to remove one election from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.

Front 36

Successive Ionisation Energy

Back 36

A measure of energy required to remove each electron in turn.

Front 37

Isotopes

Back 37

Atoms of the same element with different numbers of neutrons and different masses.

Front 38

Lone Pair

Back 38

An outer shell pair of electrons that is not involved in chemical bonding.

Front 39

Mass Number/Nucleon Number

Back 39

The number of particles (Protons and Neutrons) in the nucleus.

Front 40

Metallic Bond

Back 40

The electrostatic attraction between positive metal ions and delocalised electrons.

Front 41

Molar Mass, M

Back 41

The mass per mole of a substance. The units of Molar Mass are g mol^-1 (g/mol).

Front 42

Molar Volume

Back 42

The volume per mole of a gas. The units of molar volume are in dm^3 mol^-1. At room temperature and pressure the molar volume is approximately 24.0 dm^3 mol^-1.

Front 43

Mole

Back 43

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

Front 44

Molecular Formula

Back 44

The number of atoms of each element in a molecule

Front 45

Molecular Ion M+

Back 45

The positive ion formed in mass spectromotery when a molecule loses an electron.

Front 46

Molecule

Back 46

A small group of atoms held together by covalent bonds.

Front 47

Oxidation

Back 47

Loss of electrons or an increase in oxidation number.

Front 48

Oxidation Number

Back 48

A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of molecules.

Front 49

Oxidising agent

Back 49

A reagent that oxidises (takes electrons from) another species.

Front 50

Percentage Yield

Back 50

% yield = (actual amount, in mol, of product) / (theoretical amount, in mol, of product) x 100

Front 51

Period

Back 51

A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period.

Front 52

Periodicity

Back 52

A regular periodic variation of properties of element with atomic number and position in the Periodic Table.

Front 53

Permanent dipole

Back 53

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

Front 54

Permanent dipole-dipole force

Back 54

An attractive force between permanent dipoles in neighbouring polar molecules.

Front 55

Polar Covalent Bond

Back 55

A bond with a permanent dipole.

Front 56

Precipitation Reaction

Back 56

The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together.

Front 57

Principle Quantum Number, n

Back 57

A number representing the relative overall energy of each orbital which increases with distance from the nucleus. The sets of orbitals with the same n value are referred to as electron shells or energy levels.

Front 58

Rate of Reaction

Back 58

The change in concentration of a reactant or a product in a given time.

Front 59

Redox Reaction

Back 59

A reaction in which both reduction and oxidation take place.

Front 60

Reducing Agent

Back 60

A reagent that reduces (adds electrons to) another species.

Front 61

Reduction

Back 61

Gain of electrons or a decrease in oxidation number.

Front 62

Relative Atomic Mass

Back 62

The weighted mean mass of an element compared with one-twelfth of the mass of an atom of carbon-12.

Front 63

Relative Formula Mass

Back 63

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

Front 64

Relative Isotopic Mass

Back 64

The weighted mean mass of an isotope compared with one-twelfth of the mass of an atom of carbon-12.

Front 65

Relative Molecular Mass

Back 65

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

Front 66

Salt

Back 66

A chemical compound formed from an acid, when a H+ ion from the acid has been replaced by a metal ion or another positive ion, such as the ammonium ion NH4+.

Front 67

Shell

Back 67

A group of atomic orbitals with the same principal quantum number, n. Also known as a main energy level.

Front 68

Simple Molecular Lattice

Back 68

A three-dimensional structure of molecules, bonded together by weak intermolecular forces.

Front 69

Species

Back 69

Any type of particle that takes part in a chemical reaction.

Front 70

Spectator Ions

Back 70

Ions that are present but take no part in a chemical reaction.

Front 71

Standard Conditions

Back 71

A pressure of 1--kPa (1 atmosphere), a stated temperature, usually 298K, and a concentration of 1 mol dm^-3 (for reactions with aqueous solutions).

Front 72

Standard Solution

Back 72

A solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about another substance.

Front 73

Standard State

Back 73

The physical state of a substance under the standard conditions of 100kPa (1 atmosphere) and 298K.

Front 74

Sub-Shell

Back 74

A group of the same type of atomic orbitals (s, p, d or f) within a shell.

Front 75

van der Waals' forces

Back 75

Very weak attractive forces between induced dipoles in neighbouring molecules.

Front 76

Volatility

Back 76

The ease with which a liquid turns into a fas. Volatility increases as boiling point decreases.

Front 77

Water of Crystallisation

Back 77

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