# Definitions- Unit 1 Module 1 (Atoms and reactions)

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• Created by: komahinae
• Created on: 03-03-15 17:36
Isotopes
Atoms of the same element with different numbers of neutrons
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Atomic (proton) number
The number of protons in the nucleus of an atom
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Mass (nucleon) number
The number of particles (protons and neutrons) in the nucleus
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Ion
A positively or negatively charged atom or (covalently bonded) group of atoms (a molecular ion)
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Relative isotopic mass
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12
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Relative atomic mass (Ar)
The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12
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Relative molecular mass (Mr)
The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12
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Relative formula mass
The weighted mean mass of a formula unit compared with one-twelfth of the mass of an atom of carbon-12
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Amount of substance
The quantity whose unit is the mole. Chemists use 'amount of substance' as a means of counting atoms
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Avogadro constant (NA)
The number of atoms per mole of the carbon-12 isotope (6.02 x 10^23/mol)
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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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Molar mass (M)
The mass per mole of a substance. The units of molar mass are g/mol)
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Empirical formula
The simplest whole-number ratio of atoms of 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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Molar volume
The volume per mole of a gas. The units of molar volume are dm^3/mol. At room temperature and pressure, the molar volume is approximately 24.0 dm^3/mol
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Concentration of a solution
The amount of solute, in mol, dissolved per 1dm^3 (1000cm^3) of solution
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Standard solution
A solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about another substance
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Species
Any type of particle that takes place 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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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, OH-(aq)
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Salt
Any chemical compound formed from an acid when a H+ ion from the acid has been replaced by a metal ion or other positive ion
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Hydrated
Refers to a crystalline compound containing water molecules
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Anhydrous
A substance that contains no water molecules
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Oxidation number
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.
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Oxidation
Loss of electrons or an increase in oxidation number
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Reduction
Gain of electrons or a decrease in oxidation number
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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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Oxidising agent
A reagent that oxidises (takes electrons from) another species
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## Other cards in this set

### Card 2

#### Front

The number of protons in the nucleus of an atom

#### Back

Atomic (proton) number

### Card 3

#### Front

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

### Card 4

#### Front

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

### Card 5

#### Front

The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12

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