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AS Chemistry (definitions) > Definitions - Atoms, Bonds & Groups > Flashcards

Definitions - Atoms, Bonds & Groups Flashcards

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1
Q

Acid

A

A species that is a proton (H+) donor.

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2
Q

Alkali

A

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

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3
Q

Amount of substance

A

The quantity whose unit is the mole. Chemists use “amount of substance” as a means of counting atoms.

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4
Q

Anhydrous

A

A substance which contains no water molecules.

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5
Q

Anion

A

A negatively charged ion.

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6
Q

Atomic orbital

A

Region within an atom which can hold up to two electrons, opposite spin.

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7
Q

Atomic number

A

The number of protons in the nucleus of an atom.

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8
Q

Avogadro Number (N_A)

A

The number of atoms per mole of the carbon-12 isotope (6.02 x 10^23 mol^-1)

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9
Q

Base

A

A species that is a proton (H+) acceptor.

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10
Q

Cation

A

A positively charged ion.

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11
Q

Compound

A

A substance formed from two or more chemically bonded elements in a fixed ratio; usually shown by a chemical formula.

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12
Q

Concentration

A

The amount of solute, in moles, per cubic decimeter of solution.

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13
Q

Coordinate Bond (= Dative Bond)

A

A shared pair of electrons which has been provided by one of the bonding atoms only (also called a Dative bond).

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14
Q

Dehydration

A

An elimination reaction in which water is removed from a saturated molecule to make it unsaturated.

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15
Q

Delocalised electrons

A

Electrons which are shared between more than two atoms.

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16
Q

Displacement reaction

A

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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17
Q

Disproportionation

A

The oxidation and reduction of the same element in a redox reaction.

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18
Q

Electron configuration

A

The arrangement of electrons in an atom.

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19
Q

Electronegativity

A

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

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20
Q

Electron Shielding

A

The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons.

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21
Q

Empirical formula

A

The simplest whole number ratio of atoms of each element present in a compound.

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22
Q

Giant covalent lattice

A

A three-dimensional structure of atoms, bonded by strong covalent bonds.

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23
Q

Giant ionic lattice

A

A three-dimensional structure of oppositely charged ions, bonded together by strong ionic bonds.

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24
Q

Giant metallic lattice

A

A three-dimensional structure of positive metal ions and delocalised electrons, bonded together by strong metallic bonds.

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25
Q

Group

A

A vertical column in the periodic table. Elements in the same group have similar chemical properties and have the same number of outer shell electrons.

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26
Q

Hydrogen bond

A

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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27
Q

Intermolecular force

A

An attractive force between neighbouring molecules. Intermolecular forces can be van der Waals’ forces (induced dipole-dipole forces), permanent dipole-dipole forces or hydrogen bonds.

28
Q

Ion

A

A positively or negatively charged atom or (covalently bonded) group of atoms (a molecular ion).

29
Q

Ionic Bonding

A

The electrostatic attraction between oppositely charged ions.

30
Q

First Ionisation Energy

A

The energy required to remove 1 electron from each atom in 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions.

31
Q

Second Ionisation Energy

A

The energy required to remove 1 electron from each ion in 1 mol of gaseous 1+ ions to form 1 mol of gaseous 2+ ions.

32
Q

Successive Ionisation Energy

A

A measure of the energy required to remove 1 electron in turn; e.g. the second ionisation energy is the energy required to remove 1 electron from each ion in 1 mol of gaseous 1+ ions to form 1 mol of gaseous 2+ ions.

33
Q

Isotopes

A

Atoms of the same element with a different number of neutrons.

34
Q

Lone pair

A

An outer-shell pair of electrons not involved in chemical bonding.

35
Q

Mass (nucleon number)

A

The number of particles (protons and neutrons) in the nucleus.

36
Q

Metallic bonding

A

The electrostatic attraction between the positive metal ions and delocalised electrons.

37
Q

Molar mass (M_R)

A

The mass per mole of substance. The units of molar mass are g/mol.

38
Q

Molar volume

A

The volume per mole of gas. The units of molar volume are cubic decimeter per mole (dm^3/mol). At room temperature and pressure the molar volume is approximately 24.0 dm^3/mol.

39
Q

Mole

A

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

40
Q

Oxidation

A

Loss of electrons or an increase in oxidation number.

41
Q

Oxidation number

A

A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules.

42
Q

Oxidising agent

A

A reagent that oxidises (takes electrons from) another species.

43
Q

Period

A

A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period.

44
Q

Periodicity

A

A regular periodic variation of properties of elements with atomic number and position in the Periodic Table.

45
Q

Permanent dipole

A

A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms.

46
Q

Permanent dipole-dipole force

A

An attractive force between permanent dipoles in neighbouring polar regions.

47
Q

Polar covalent bond

A

A bond with a permanent dipole.

48
Q

Polar molecule

A

A molecule with an overall dipole, taking into account any dipoles across bonds.

49
Q

Precipitation reaction

A

The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together.

50
Q

Principal quantum number, n

A

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 electrons shells or energy levels.

51
Q

Redox reaction

A

A reaction in which both reduction and oxidation take place.

52
Q

Reducing agent

A

A reagent that reduces (adds electrons to) another species.

53
Q

Relative atomic mass

A

The weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon-12.

54
Q

Relative formula mass

A

The weighted mean mass of a formula unit compared with 1/12 of the mass of an atom of carbon-12.

55
Q

Relative isotopic mass

A

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

56
Q

Relative molecular mass

A

The weighted mean mass of a molecule compared with 1/12 of the mass of an atom of carbon-12.

57
Q

Salt

A

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 (such as the ammonium ion, NH4+)

58
Q

Shell

A

A group of atomic orbitals with the same principal quantum number, n. Also known as a main energy level.

59
Q

Simple molecular lattice

A

A three-dimensional lattice of molecules, bonded together by weak intermolecular forces.

60
Q

Species

A

Any type of particle that takes part in a chemical reaction.

61
Q

Spectator ions

A

Ions that are present but take no part in a chemical reaction.

62
Q

Standard solution

A

A solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about another substance.

63
Q

Sub-shell

A

A group of the same type of atomic orbitals (s, p, d or f) within a shell.

64
Q

Substitution reaction

A

A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms/

65
Q

Thermal decomposition

A

The breaking up of a chemical substance with heat into at least two chemical substances.

66
Q

van der Waals’ force

A

Very weak attractive forces between induced dipoles in neighbouring molecules.

67
Q

Water of crystallisation

A

Water molecules that form an essential part of the crystalline structure of a compound.

AS Chemistry (definitions) (2 decks)

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