Chemistry: Atoms, Bonds and Groups Definitions

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Isotope
Atoms of the same element with different numbers of neutrons.
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Ion
A positively or negatively charged atom or group of atoms.
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Relative isotopic mass
The mass of an isotope compared with 1/12th the mass of an atom of carbon-12.
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Relative atomic/molecular/formula mass
The weighted mean mass of an atom/molecule/formula unit compared to 1/12th of the mass of an atom of carbon-12.
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Mole
The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.
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Empirical formula
The simplest whole-number ratio of atoms or each element present in a compound.
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Molecule
A small group of atoms held together by covalent bonds.
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Molecular formula
The actual number of atoms of each element in a molecule.
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Standard solution
A solution of known concentration.
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Species
Any type of particle that takes place in a reaction.
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Stoichiometry
The molar relationship between the relative quantities of substance taking part in a reaction.
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Acid
A species that is a proton donor.
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Base
A species that is a proton acceptor.
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Alkali
A type of base that dissolves in water forming hydroxide ions.
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Salt
A chemical compound formed from an acid when a H+ ion from the acid has been replaced by a metal ion or another positive ion.
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Anhydrous
A substance that contains no water molecules
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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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Oxidation
Loss of electrons/Increase of oxidation number.
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Reduction
Gain of electrons/Decrease in oxidation number.
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Reducing Agent
A reagent that reduces (adds electrons to) another species.
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Oxidising Agent
Reagent that oxidises (takes electrons from) another species.
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First ionisation energy.
The energy required to remove one electron from each atom in one mole of gaseous atoms to from 1 mole of gaseous 1+ ions.
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Electron shielding
The repulsion between electrons in different inner shell. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons.
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Successive ionisation energies
A measure of the energy required to remove each electron in turn.
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Shell
A group of atomic orbitals all with the same principle quantum number, n, known as a main energy level.
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Principle quantum number
A number representing the relative overall energy of each orbital, which increases with distance from the nucleus.
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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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Sub-shell
A group with the same type of atomic orbitals (s, p, d or f) within a shell.
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Electron Configuration
The arrangement of electrons in an atom.
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Compound
A substance found from two or more chemically bonded elements in a fixed ration.
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Ionic Bond
The electrostatic attraction between oppositely charged ions.
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Giant ionic lattice
A 3-D structure of oppositely charged ions, held together by strong ionic bonds.
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Group
A vertical column in the periodic table. All the atoms of the elements have the same number of outer-shell electrons.
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Covalent bond
A bond formed by a shared pair of electrons.
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Lone pair
An outer shell pair of electrons that is not involved in chemical bonding.
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Dative covalent/coordinate bond
A shared pair of electrons which has been provided by one of the bonding atoms only.
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Electronegativity
The measure of attraction of a bonded atom for a pair of electrons in a covalent bond.
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Permanent dipole
A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms.
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Polar molecule
Has an overall dipole.
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Intermolecular force
An attractive force between neighbouring molecules.
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Permanent dipole-dipole force
A weak attractive force between permanent dipoles in neighbouring polar molecules.
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Van der Waals' forces
Attractive forces between induced dipole in neighbouring molecules.
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Metallic bonding
The electrostatic attraction between positive metal ions and delocalised electrons.
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Delocalised electrons
Are shared between more than two atoms.
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Giant metallic lattice
A 3-D structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.
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Simple molecular lattice
A 3-D structure of molecules bonded together by weak intermolecular forces.
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Giant covalent lattice
A 3-D structure of atoms, bonded together by strong covalent bonds.
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Period
Horizontal row on the periodic table. All the elements in a period have atoms with the same number of electron shells.
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Periodicity
Regular periodic variation of properties of elements with atomic number and position in the periodic table.
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Thermal decomposition
The breaking up of a chemical substance with heat into at least two chemical substances.
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Displacement reaction
A reaction in which a more-reactive element displaces the 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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Redox reaction
The oxidation and reduction of 1 or more elements within a reaction
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Precipitation reaction
The formation of a solid from a solution during a chemical reaction.
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Fluorine
Called the Tyrannosaurus-rex of the elements.
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Other cards in this set

Card 2

Front

A positively or negatively charged atom or group of atoms.

Back

Ion

Card 3

Front

The mass of an isotope compared with 1/12th the mass of an atom of carbon-12.

Back

Preview of the back of card 3

Card 4

Front

The weighted mean mass of an atom/molecule/formula unit compared to 1/12th of the mass of an atom of carbon-12.

Back

Preview of the back of card 4

Card 5

Front

The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.

Back

Preview of the back of card 5
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