Chemistry Definitions

Made specifically for AS level Chemistry, OCR

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  • Created by: Molly
  • Created on: 01-11-12 12:38
Atomic (proton) Number
Number of protons in the nucleus of an atom
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Mass (Nucleon) Number
Number of particles (protons and neutrons) in an atom
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Isotopes
Atoms of the same element with different numbers of neutrons
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Ion
Positively or negatively charged atom or (covelently bonded) group of atoms (a molecular ions)
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Relative Isotopic mass
The mass of an atom of an isotope compared with 1/12 of the mass of an atom of carbon-12
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Relative atomic mass
the weighted average mass of an atom of an element compared with 1/12 of the mass of the atom carbon-12
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Relative molecular mass
The weighted average mass of a molecule compared with 1/12 of the mass of an atom of C-12
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Relative formular mass
the weighted mean mass of a formula unit compared with 1/12 of the mass of an atom of C-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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Avagadro Constant
the number of atoms per mole of the C-12 isotope (6.02x10^23)
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Mole
the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the C-12 isotope
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Molar Mass (M)
the mass per mole of a substance. Units are g mol^-1
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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
Small group of atoms held together by a covalent bond
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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^-1. At room temp and oressure the molar volume is approx. 24.0 dm^3mol^-1
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Concentration of a solution
amount of solute, in mol, dissolved per dm^3 of solution
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Standard Solution
solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about the other substance
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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 increase of oxidation number
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Reduction
gain of electrons or decrease of oxidation number
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Reducing agent
reagent that reduces (adds electron to) another species
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Oxidising agent
a reagent that oxidises (takes electrons from) another species
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First Ionisation Energy
the energy required to remove one electron from the outer shell of each atom in 1 mol of gaseous atoms. Forming 1 mol of gaseous 1+ ions.
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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 electrons
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Successive ionisation energies
measure of energy required to remove each electron in turn
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Shell
a group of orbitals with the same principal quantum number.
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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 orbitals with the same n-value are reffered to as electron shells or energy levels.
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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 of the same type of atomic orbitals (s,p,d or f) within a shell
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Electron Configuration
arrangement of electrons within an atom
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Compound
substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula
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Giant Ionic Lattice
a three-dimensional structure of oppositely charged ions held together by strong ionic bonds
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Group
verticle column in the PT. Elements in the group have similar chemical properties and their atoms have the same number of outer-shell electrons
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Covalent bond
bond formed by a shared pair of electrins
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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 atoms that has been provided for by one of the bonding atoms only
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Other cards in this set

Card 2

Front

Number of particles (protons and neutrons) in an atom

Back

Mass (Nucleon) Number

Card 3

Front

Atoms of the same element with different numbers of neutrons

Back

Preview of the back of card 3

Card 4

Front

Positively or negatively charged atom or (covelently bonded) group of atoms (a molecular ions)

Back

Preview of the back of card 4

Card 5

Front

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

Back

Preview of the back of card 5
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