Chemistry Key Definitions (OCR)

Description

Key Definition flashcards for those that struggle to learn them by looking at an A4 sheet.
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Flashcards by 20255996, updated more than 1 year ago
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Created by 20255996 over 8 years ago
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Resource summary

Question Answer
Atomic Number The number of protons in the nucleus of an atom.
Mass Number The number of protons and neutrons in the nucleus of an atom.
Relative Isotopic Mass The mass of an atom of an isotope compared with 1/12 of the mass of an atom of C-12.
Relative Atomic Mass The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of C-12.
Isotopes Atoms of the same element with a different number of neutrons.
Mole The amount of substance containing as many particles as there are carbon atoms in exactly 12g of C-12.
Avogadro's Constant The number of particles per mole of a substance. (6.02 x 10^23)
Molar Mass The mass, in g, per mole of a substance. Units are gmol-1.
Empirical Formula The simplest whole number ratio of atoms of each element present in a compound.
Molecular Formula The actual number of atoms of each element in a molecule.
Water of Crystallisation The water present in a compound giving the compound a crystalline appearance.
Acid Releases H+ ions in solution. (Proton donor)
Base A proton acceptor.
Alkali A soluble base that releases OH- ions when in solution.
Salt A compound produced when a H+ ion from an acid is replaced by a metal ion or another positive ion, such as the ammonium ion.
Anhydrous When all the waters of crystallisation have been removed from a compound.
Hydrated When water of crystallisation is present in a crystal compound.
Oxidation Number A measure of the number of electrons that an atom uses to bond with atoms of a different element.
Oxidation The loss of electrons/an increase in oxidation number (state).
Oxidising Agent A reagent which oxidises another species (gets reduced itself).
Reduction The gain of electrons/a decrease in oxidation number (state).
Reducing Agent A reagent that reduces another species (gets oxidised itself).
Redox A reaction were both oxidation and reduction take place.
Displacement Reaction A reaction in which a more reactive element displaces a less reactive element from aqueous solution of its halide ions.
Disproportionation A reaction in which an element is simultaneously oxidised and reduced.
Atomic Orbital A region within an atom that can hold up to 2 electrons, with opposite spins.
S/P/D Block Element Highest energy sub–shell is an S/P/D sub-shell.
Ionic Bond The electrostatic attraction between oppositely charged ions.
Covalent Bond The sharing of a pair of electrons between two atoms.
Dative (Co-Ordinate) Bond The sharing of a pair of electrons between two atoms where only one of the atoms supplies both the electrons shared.
Electronegativity The ability of an atom to attract the bonding electrons towards itself in a covalent bond.
Metallic Bonding The attraction of positive metal ions to delocalised electrons.
Periodicity The repeating pattern of trends across different periods.
Hydrogen Bond A dipole-dipole attraction between a slightly positive hydrogen on one molecule and a lone pair of electrons on a highly electronegative atom (N, O, F) of another molecule.
First Ionisation Energy The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions. Units are kJmol-1.
Successive Ionisation Energy A measure of the energy required to remove each electron in turn.
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