MUST KNOW Definitions Flashcards

1
Q

Relative Atomic Mass Ar

A

the weighted average of the masses of its isotopes relative to 1/12 of the mass of a C12 atom

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2
Q

Relative Molecular Mass Mr

A

the weighted average of the masses of the atoms in a molecule relative to 1/12 of the mass of a C12 atom

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3
Q

Mass Number (A)

A

the sum of protons and neutrons in the nucleus of an atom

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4
Q

Atomic Number (Z)

A

the number of protons in the nucleus of an atom

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5
Q

Isotopes

A

atoms with the same atomic number but a different mass number

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6
Q

Empirical Formula

A

the simplest whole number ratio of elements in a compound

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7
Q

Molecular Formula

A

the actual number of atoms of each element in the formula of a compound

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8
Q

Ionic Bond

A

Oppositely charged ions held together by an electrostatic attraction

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9
Q

Covalent Bond

A

the electrostatic attraction between a positively charged nucleus and a shared pair of electrons, one electron supplied by each atom either side of the bond

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10
Q

Dative Bond

A

a shared pair of electrons, both electrons being supplied by one atom in the bond

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11
Q

First Ionisation Energy

A

the minimum amount of energy required in order to remove one mole of gaseous electrons from one mole of gaseous atoms to form one mole of gaseous positive ions

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12
Q

Electronegativity

A

the ability of an atom to attract the pair of electrons in a covalent bond to itself

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13
Q

Electron Affinity

A

The enthalpy change when one mole of gaseous atoms acquires one mole of electrons to form one mole of gaseous negative ions

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14
Q

Exothermic Reaction

A

the heat of a reaction is given out to the surroundings

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15
Q

Endothermic Reaction

A

the heat of a reaction is absorbed from the surroundings

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16
Q

Average Bond Enthalpy

A

The energy required to break one mole of a particular covalent bond in the gaseous state to form gaseous atoms (under standard conditions)
it is an average value as it will be affected by neighbouring atoms

16
Q

Standard Enthalpy Change of a Reaction

A

the heat energy change under standard conditions (P= 100 kPa T=298K)

17
Q

Standard State

A

the state of an allotrope of an element or compound at standard conditions

18
Q

Standard Enthalpy of Formation

A

the enthalpy change when one mole of compound is formed in its standard state from its elements in the standard states

19
Q

Standard Enthalpy of Combustion

A

the enthalpy change when one mole of a substance undergoes complete combustion in its standard state (at STP)

20
Q

Standard Enthalpy of Atomisation

A

the enthalpy change when one mole of gaseous atoms is formed from the elements in its standard states (at STP)

20
Q

Lattice Enthalpy

A

the amount of energy required to dissociate one mole of an ionic compound to its gaseous ions (at STP)

21
Q

Electron Affinity

A

the enthalpy change when one mole of gaseous atoms accepts a mole of gaseous electrons (at STP)

22
Q

Rate of Reaction

A

change in concentration of reactant (or product) with time

23
Activation Energy
the minimum amount of energy that colliding reactants require to exceed in order for a reaction to occur
24
Oxidation
the loss of electrons gain of oxygen loss of hydrogen
25
Reduction
the gain of electrons the loss of oxygen the gain of hydrogen
26
Oxidising Agent
causes the other reacting species to be oxidised and itself reduced
27
Reducing Agent
causes the other reacting species to be reduced and itself oxidised
28
Delocalisation
electrons in p orbitals forming pi bonds but shared between more than two nuclei
29
Resonance
when more than one Lewis Structure can represent the position of a double bond
30
Sigma Bond
Results in the axial (end to end) overlap of orbitals, electron density is concentrated between the nuclei of bonding atoms
31
Hybridisation
the mixing of atomic orbitals to form new orbitals of intermediate energy
32
Pi Bond
results in the sideways overlap of parallel p orbitals, electron density is concentrated above and below the nuclei of bonding atoms