AS Chemistry Key Terms

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Ion
When the total number of electrons in an atom is not equal to the total number of protons thus giving it a net charge.
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Relative Atomic Mass
The average mass of an atom compared to 1/12th of the mass of a carbon-12 atom.
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Molecular Formula
The formula of a molecule that shows the actual number of each type of atom in the molecule.
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Empirical Formula
The formula of a compound that shows the lowest whole number ratio of each type of atom.
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Skeletal Formula
Shows the bonds between atoms with carbon and hydrogen unlabelled.
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Structural Formula
Way of showing the structure of the compound without displaying the bonds.
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Isotopes
Atoms of the same element with the same number of protons but a different number of neutrons.
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Orbital
A region of space in which the probability of finding an electron is greater than or equal to 95%; each orbital can hold a maximum of two electrons with opposite spin.
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Ionic Bonding
The electrostatic force of attraction between oppositely charged ions arranged in a regular 3D structure called an ionic lattice.
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Covalent Bonding
A shared pair of electrons that hold two atoms together.
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Dative Bond
A shared pair of electrons that holds two atoms together plus both electron comes from one atom.
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Sigma Bond
Head on overlap of two orbitals along the inter-nuclear axis.
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Pi Bond
Parallel P-orbitals overlap ‘sideways on’, above and below the inter-nuclear axis.
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Free Radical
A species with one or more unpaired electron.
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Hydrogen Bond
Strong intermolecular force of attraction between δ+ hydrogen and a lone pair of electrons on the electronegative atoms of F, O or N.
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London Dispersion (Van der Waals) Forces
Weak intermolecular force of attraction between non-polar molecules in the solid and liquid state.
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Polar Bond
Bond in which the electrons are not equally distributed between the two atoms in the bond; the more electronegative atoms will have the greater electron density.
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Electronegativity
A measure of the ability of an atom to attract a bonding pair of electrons.
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Endothermic
Reaction in which heat energy is absorbed from the surroundings causing a temperature drop.
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Exothermic
Reaction in which heat energy is released to the surroundings causing the temperature to increase.
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Standard enthalpy of formation (∆HfѲ)
Enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions of 298K and 1 atm.
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Standard enthalpy of combustion (∆HcѲ)
Enthalpy change when one mole of a compound is completely burned in excess oxygen under standard conditions of 298K and 1atm.
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Bond Enthalpy
Energy needed to break 1 mole of a specific covalent bond between two atoms in a molecule in a gaseous state averaged over several similar compounds.
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First Ionisation Energy
The energy needed to remove one mole of the highest energy electrons from one mole of neutral atoms in the gaseous stated under standard conditions.
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Lattice Energy
Energy released when one mole of a solid ionic compound is from its constituent ions in the gaseous state under standard conditions.
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Electron Affinity
The energy released when one mole of electrons are added to one mole of atoms in the gaseous state under standard conditions.
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Activation Energy
The minimum energy needed for the reactants to react upon collision.
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Catalyst
A substance that increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy and is not consumed in the overall reaction.
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Oxidation
When a substance combines with oxygen / loses hydrogen / when a specie loses electrons.
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Reduction
When a substance loses oxygen / combines with hydrogen / when a specie gains electrons.
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Oxidising Agent
A species that causes oxidation by gaining an electron or electrons from other species and is then itself reduced.
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Reducing Agent
A species that causes reduction by donating an electron or electrons to other species and is then itself oxidised.
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Disproportionation
Simultaneous oxidation and reduction of atoms of a single chemical element in a reaction.
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Saturated
Molecules that contain only carbon-carbon single bonds.
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Unsaturated
Molecules that contain at least one carbon-carbon multiple bond.
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Homologous Series
A family of compounds with the same general formula where successive members differ by one CH2 group.
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Isomers
Forms of a compound with that same molecular formula but different structural formulae.
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Stereoisomerism
Compounds with the same molecular formula but different arrangements of atoms in space.
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Geometrical isomerism
Isomerism that occurs when atoms join in the same order but with different special arrangements.
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Condensation Reaction
When two small molecules combine to form a larger one with the elimination of a smaller molecule (such as water).
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Nucleophile
Negatively charged / neutral species that donates an electron pair to an electrophile.
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Electrophile
Participates in a chemical reaction by accepting an electron pair.
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Isoelectronic
Same number of electrons as atom.
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Primary Alcohol
Adjacent carbon to -OH group has 2 (or 3) hydrogens attached.
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Secondary Alcohol
Adjacent carbon to -OH group has 1 hydrogen attached.
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Tertiary Alcohol
Adjacent carbon to -OH group has no hydrogens attached.
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Other cards in this set

Card 2

Front

The average mass of an atom compared to 1/12th of the mass of a carbon-12 atom.

Back

Relative Atomic Mass

Card 3

Front

The formula of a molecule that shows the actual number of each type of atom in the molecule.

Back

Preview of the back of card 3

Card 4

Front

The formula of a compound that shows the lowest whole number ratio of each type of atom.

Back

Preview of the back of card 4

Card 5

Front

Shows the bonds between atoms with carbon and hydrogen unlabelled.

Back

Preview of the back of card 5
View more cards

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