Chemistry ABG definitions

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Acid
A species that is a proton donor
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Alkali
A type of base that dissolves in water forming hydroxide ions, OH-(aq)
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Amount of substance
The quantity whose unit is the mole. Used by chemists as a means of counting atoms.
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Anhydrous
A substance containing no water molecules
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Anion
A negatively charged ion
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Atomic orbital
A region within an atom that can hold up to two electrons, with opposite spins
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Atomic number
The number of protons in the nucleus of an atom
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Avagadro's constant
The number of atoms per mole of the carbon-12 isotope (6.02 x 10 ^23)
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Base
A species that is a proton acceptor
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Cation
A positively charged ion
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Compound
A substance formed from two or more chemically bonded elements in a fixed ratio, usually by a chemical formula
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Concentration of solution
The amount of solute, in mol, per 1dm^3 of solution
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Coordinate bond
Dative covalent bond
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Dative covalent bond
A shared pair of electrons which has been provided by one of the bonded atoms only
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Covalent bond
A bond formed by a shared pair of electrons
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Delocalised electrons
Electrons that are shared between more than two atoms
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Displacement reaction
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ions
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Disproportionation
The oxidation and reduction of the same element in a redox reaction
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Electron configuration
The arrangement of electrons in an atom
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Electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
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Electron shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell of electrons.
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Empirical formula
The simplest whole-number ratio of atoms of each element present in a compound
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Giant covalent lattice
A 3D structure of atoms, bonded together by strong covalent bonds
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Giant ionic lattice
A 3D structure of oppositely charged ions, bonded together by strong ionic bonds
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Giant metallic lattice
A 3D structure of positive ions and delocalised electrons, bonded together by strong metallic bonds
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Group
Vertical column in the Periodic Table. Elements in a group have similar chemical properties and their atoms have the same number of outer-shell electrons.
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Hydrated
Crystalline and containing water molecules
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Hydrogen bond
A strong dipole-dipole attraction between an electron-deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule
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Hydrolysis
A reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds
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Intermolecular force
An attractive force between neighbouring molecules. They can be van der Waals' forces (induced dipole-dipole forces), permanent dipole-dipole forces or hydrogen bonds
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Ion
A positively or negatively charged atom or group of atoms
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Ionic bond
The electrostatic attraction between oppositely charged ions
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(First) ionisation energy
The amount of energy required to remove one electron from each atom in one mole of gaseous atoms, forming one mole of gaseous 1+ ions
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(Second) ionisation energy
The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
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(Successive) ionisation energy
A measure of the energy required to remove one electron in turn
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Isotopes
Atoms of the same element with different numbers of neutrons and different masses
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Lone pair
An outer shell pair of electrons that is not involved in chemical bonding
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Mass number
The number of protons and neutrons in the nucleus of an atom
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Metallic bond
The electrostatic attraction between positive metal ions and delocalised electrons
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Molar mass
The mass per mole of a substance (gmol^-1)
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Molar volume
The volume per mole of a gas (dm^3mol^-1). At room temperature and pressure, the molar volume is (approx.) 24 dm^3mol^-1
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Mole
The amount of any substance containing the same number of particles as there are carbon atoms in exactly 12 g of the carbon-12 isoptope
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Molecular formula
The number of atoms of each element in a molecule
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Molecule
A small group of atoms held together by covalent bonds
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Oxidation
Loss of electrons or an increase in oxidation number
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Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element. They are derived from a set of rules
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Oxidising agent
A reagent that oxidises (takes electrons from) another species
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Period
A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period.
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Periodicity
A regular periodic variation of properties of elements with atomic number and position in the Periodic Table
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Permanent dipole
A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms
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Permanent dipole-dipole force
An attractive force between permanent dipoles in neighbouring molecules
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Polar covalent bond
A bond with a permanent dipole
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Precipitation reaction
The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together
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Principal quantum number, n
A number representing the relative overall energy of each orbital, which increases with distance from the nucleus. The sets of orbitals with the same n value are referred to as electron shells or enegry levels.
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Redox reaction
A reaction in which both reduction and oxidation take place
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Reducing agent
A reagent that reduces (adds electrons to) another species
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Reduction
The gain of electrons or decrease in oxidation number
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Relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12th of the mass of one atom of carbon-12
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Relative isotopic mass
The mass of an atom of an isotope compared with 1/12th the mass of one atom of carbon-12
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Relative formula mass
The weighted mean mass of a formula unit compared with 1/12th the mass of one atom of carbon-12
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Relative molecular mass, Mr
The weighted mean mass of a molecule compared with 1/12th the mass of one atom of carbon-12
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Salt
A chemical compound formed from an acid, when an H+ ion from the acid is replaced by a metal ion or another positive ion, such as the ammonium ion, NH4+
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Shell
A group of atomic orbitals with the same principal quantum number/energy level
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Simple molecular lattice
A 3D structure of molecules, bonded together by weak intermolecular forces
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Species
Any type of particle that takes part in a chemical reaction
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Spectator ions
Ions that are present but take no part in a chemical reaction
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Stoichiometry
The molar relationship between the relative quantities of substances taking part in a reaction
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Sub-shell
A group of the same type of atomic orbitals (SPDF) within a shell
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Thermal decomposition
The breaking up of a chemical substance by heat into at least two chemical substances
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van der Waals' forces
Very weak intermolecular forces between induced dipoles in neighbouring molecules
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Volatility
The ease with which a liquid turns into a gas. Volatility increases as boiling point increases
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Water of crystallisation
Water molecules that form an essential part of the crystalline structure of a compound
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Card 2

Front

A type of base that dissolves in water forming hydroxide ions, OH-(aq)

Back

Alkali

Card 3

Front

The quantity whose unit is the mole. Used by chemists as a means of counting atoms.

Back

Preview of the back of card 3

Card 4

Front

A substance containing no water molecules

Back

Preview of the back of card 4

Card 5

Front

A negatively charged ion

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Preview of the back of card 5
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