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Edexcel A-Level Chemistry > Definitions > Flashcards

Definitions Flashcards

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1
Q

Atomic number (z)

A

the number of protons in the nucleus of an atom

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2
Q

Mass number (a)

A

the total number or protons and neutrons in the nucleus of an atom

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3
Q

Relative isotopic mass (RIM)

A

the mass of an atom of a particular isotope of an element, relative to 1/12th the mass of a carbon-12 atom

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4
Q

Relative atomic mass (RAM, Ar)

A

the average mass of an atom of an element, relative to 1/12th the mass of a carbon-12 atom

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5
Q

Orbital

A

a region of 3D in which there is a probability of finding an electron

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6
Q

1st ionisation energy

A

energy required to remove one electron from each atom, in a mole of gaseous atoms

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7
Q

2nd ionisation energy

A

energy required to remove one electron from each 1+ ion, in a mole of gaseous 1+ ions

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8
Q

Periodicity

A

trends in the properties of elements repeat in successive periods of the periodic table

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9
Q

Electronegativity

A

the ability of an atom of an element to attract a pair of bonding electrons

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10
Q

Oxidised

A

loss of electrons and increase in oxidation number

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11
Q

Reduced

A

gain of electrons and decrease in oxidation number

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12
Q

Oxidising agent

A

causes oxidation by taking away electrons

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13
Q

Reducing agent

A

causes reduction by giving electrons

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14
Q

Hess’s law

A

ΔH for a reaction is independent of the route taken

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15
Q

Standard enthalpy of formation

A

enthalpy change when one mole of a substance is formed from its elements in their standard states at 298K and 100kPa

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16
Q

Standard enthalpy of combustion

A

enthalpy change when one mole of a substance is completely oxidised in excess oxygen at standard conditions 298K and 100kPa

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17
Q

Why do we do Hess cycles

A

when it requires heat energy and we cant measure temp change

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18
Q

Mole

A

the amount of any substance which occupies a volume of 24dm3 at room temp and pressure

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19
Q

Avogadros number

A

the number of things in a mole

20
Q

Ionic bonding

A

the electrostatic attraction between oppositely charged ions in all directions

21
Q

Anions

A

negative ions

22
Q

Cations

A

positive ions

23
Q

Covalent bonding

A

the electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

24
Q

Dative bond

A

is a covalent bond where only one of the bonded atoms donated both electrons being shared

25
Q

Symmetrical molecule

A

all the atoms around the central atom are the same and there are no lone pairs on the central atom

26
Q

Unsymmetrical molecule

A

the central atom has two or more different atoms or the central atoms has one or more lone pairs

27
Q

Disproportionation

A

A reaction where one element in one species is both oxidised and reduced

28
Q

Lattice energy (LE)

A

Energy released when one mole of an ionic compound is formed from gaseous ions

29
Q

Standard enthalpy of hydration

A

Enthalpy change when one mole of gaseous ions are hydrated by excess water

30
Q

Standard enthalpy of solution

A

Enthalpy change when on mole of ionic solid dissolves in excess water

31
Q

What is entropy

A

A measure of the amount of disorder

32
Q

Rate or reaction

A

Change in quantity of reactant or product over time

33
Q

Activation energy

A

The minimum energy required for a collision to be successful

34
Q

Homogenous catalyst

A

Catalyst is in the same state/phase as the reactants

35
Q

Heterogenous catalyst

A

The catalyst is in a different phase from reactants

36
Q

Adsorption

A

A process in which atoms, molecules or ions are held on the surface of the solid

37
Q

Desorption

A

Removal of an adsorbed molecule, atom or ion from an adsorbent

38
Q

Half life

A

Time taken for the concentration of reaction to halve

39
Q

Chiral molecule

A

A molecule containing a carbon atom which has four different groups bonded to it

40
Q

Stability constant Kstab

A

The equilibrium constant for the formation of a complex ion in a solvent from its constituent ions

41
Q

Large Kstab

A

stable complex

42
Q

Small Kstab

A

unstable complex

43
Q

Standard electrode potential

A
  • The emf of a half cell measured relative to the standard hydrogen electrode
  • All solutions at 1moldm-3 concentration and gases at 100kPa
  • At 298 K
44
Q

Lattice enthalpy of formation

A

Enthalpy change when:
- 1 mole of a solid ionic compound is formed
- from its gaseous ions
- under standard conditions

45
Q

Enthalpy change of atomisation

A

Enthalpy change when:
- 1 mole of gaseous atoms is made
- from an element
- in its standard state

46
Q

Enthalpy change of solution

A

Enthalpy change when:
- 1 mole of an ionic substance is dissolved in the minimum amount of solvent
- to ensure no further enthalpy change is observed upon further dilution

Edexcel A-Level Chemistry (16 decks)

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