Glossary

Question 1

Agonist

Answer 1

a drug which enhances the body’s natural response or mimics the natural response of the body

Question 2

Amphoteric

Answer 2

a substance which can act as both an acid and a base

Question 3

Antagonist

Answer 3

a drug which blocks the natural response of the body

Question 4

Aromatic

Answer 4

aromatic compounds contain a benzene ring in their structure

Question 5

Aufbau principle

Answer 5

states that orbitals are filled in order of increasing energy

Question 6

Avogadro’s constant

Answer 6

the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole ( L = 6.02 × 1023 mol-1)

Question 7

Buffer solution

Answer 7

a solution in which the pH remains approximately constant when small amounts of acid or base are added

Question 8

Carbocation

Answer 8

an ion with a positively charged carbon atom

Question 9

Chiral

Answer 9

A chiral molecule is one which has a non-superimposable mirror image, i.e. optical isomers exist. All chiral molecules have a chiral carbon atom, i.e. a carbon atom with four different atoms or groups bonded to it

Question 10

Chromophore

Answer 10

the group of atoms within a molecule which is responsible for the absorption of light in the visible spectrum. Molecules containing a
chromophore are coloured

Question 11

Cis

Answer 11

cis molecules have two of the same atom or group on the same side of a carbon-to-carbon double bond

Question 12

Closed

Answer 12

a closed system has no exchange of matter or energy with its surroundings

Question 13

Conjugate acid

Answer 13

the species left when a base accepts a proton

Question 14

Conjugate base

Answer 14

the species formed when an acid donates a proton

Question 15

Conjugated

Answer 15

conjugated systems contain delocalised electrons spread over a few atoms. This is often through alternating single and double bonds

Question 16

Coordination number

Answer 16

the number of bonds a transition metal ion forms with surrounding ligands

Question 17

Dative

Answer 17

a bond where both electrons have come from one of the elements involved in the bond

Question 18

Degenerate

Answer 18

a set of atomic orbitals that are of equal energy to each other are said to be degenerate

Question 19

Dynamic equilibrium

Answer 19

a dynamic equilibrium is achieved when the rates of two opposing processes become equal, so that no net change results

Question 20

Electromagnetic spectrum

Answer 20

the range of frequencies or wavelengths of electromagnetic radiation

Question 21

Electrophile

Answer 21

a species which is attracted to an electron rich site; electrophiles are electron deficient and have a positive charge

Question 22

Electrophilic addition

Answer 22

addition across a carbon-to-carbon double bond

Question 23

Electrophilic substitution

Answer 23

substitution of a hydrogen atom on a benzene ring for an electrophile

Question 24

Enantiomers

Answer 24

optical isomers
(non-superimposable mirror images) are known as enantiomers.

Question 25

Enthalpy of formation

Answer 25

the enthalpy change when one mole of a substance is formed from its elements in their standard states

Question 26

Entropy

Answer 26

the degree of disorder of a system

Question 27

Equivalence point

Answer 27

the equivalence point in a titration experiment is reached when the reaction between the titrant (added from the burette) and the titrate (in the flask) is just complete.

Question 28

Free energy

Answer 28

the total amount of energy available to do work

Question 29

Frequency

Answer 29

the number of wavelengths that pass a fixed point in one unit of time, usually one second

Question 30

Ground state

Answer 30

the lowest possible electronic configuration the electrons in an atom can adopt

Question 31

Heisenberg’s uncertainty principle

Answer 31

states that it is impossible to state precisely the position and the momentum of an electron at the same instant

Question 32

HOMO

Answer 32

highest occupied molecular orbital

Question 33

Hund’s rule

Answer 33

when degenerate orbitals are available, electrons fill each singly, but keeping their spins parallel before pairing starts

Question 34

Inhibitor

Answer 34

A drug which binds to the active site of an enzyme and blocks the reaction normally catalysed there.

Question 35

Ionic product of water

Answer 35

K w = [H3O+][OH-] = 1 × 10-14 at 298 K

Question 36

Ionisation energy

Answer 36

the first ionisation energy of an element is the energy required to remove one electron from each of one mole of atoms in the gas phase to form one mole of the positively charged ions in the gas phase

Question 37

Ligand

Answer 37

an ion or molecule which can bind to a transition metal ion to form a complex: ligands have a negative charge or at least one lone pair of electrons

Question 38

LUMO

Answer 38

lowest unoccupied molecular orbital

Question 39

Nucleophile

Answer 39

a species which is attracted to a positive charge; nucleophiles are electron rich species, i.e. they have a negative charge or lone pairs of electrons

Question 40

Nucleophilic substitution

Answer 40

a reaction in which one atom or group of atoms is substituted by a nucleophile

Question 41

Parent ion

Answer 41

a molecular ion produced during electron bombardment in mass spectrometry. In a mass spectrum the peak with the largest m/z
value represents the parent ion and therefore the molecular mass of the molecule

Question 42

Pauli exclusion principle

Answer 42

states that no two electrons in the one atom can have the same set of four quantum numbers - as a consequence, no orbital can hold more than two electrons and the two electrons must have opposite spins

Question 43

Planck’s constant

Answer 43

the physical constant that is the quantum of action in quantum mechanics ( h = 6.63 × 10-34 J s)

Question 44

Racemic mixture

Answer 44

a racemic mixture contains equal concentrations of both optical isomers. Racemic mixtures have no effect on plane polarised light

Question 45

Rate determining step

Answer 45

the slowest step in a reaction mechanism that governs the overall rate

Question 46

S N1

Answer 46

nucleophilic substitution, 1st order. Tertiary halogenoalkanes are likely to take part in S N1 reactions, although the kinetics of these reactions can only be determined through experimental results and not by the structure alone

Question 47

S N2

Answer 47

nucleophilic substitution, 2nd order. Primary halogenoalkanes are likely to take part in S N2 reactions, although the kinetics of these reactions can only be determined through experimental results and not by the structure alone

Question 48

Second law of thermodynamics

Answer 48

the total entropy of a reaction system and its surroundings always increases for a spontaneous change

Question 49

Spectrochemical series

Answer 49

a list of ligands according to how strongly they split d orbitals in a transition metal complex. From largest to smallest splitting ability CN - > NO2- > NH3 > H2O > OH- > F- > Cl- > Br- > I-

Question 50

Standard conditions

Answer 50

298 K (25°C) and one atmosphere pressure

Question 51

Trans

Answer 51

trans molecules have two of the same atom or group on opposite sides of a carbon-to-carbon double bond

Question 52

Velocity

Answer 52

the physical vector quantity which needs both magnitude and direction to define it, usually measured in m s -1 (or m/s)

Question 53

Wavelength

Answer 53

the distance between adjacent crests (or troughs) and is usually measured in metres or nanometres (1 nm = 10 -9 m)