Chemistry Unit 1 DEFINITIONS EDEXCEL

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Atom
The smallest particle of an element
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Element
the simplest chemicals- they cannot be broken down into simpler chemicals.
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ion
An atom, or group of atoms, which has become electrically charged by loss or gain of one or more electrons
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molecule
a particle containing two or more atoms joined together chemically
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compound
chemicals containing two or more elements chemically combined together
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empirical formula
the simplest whole number ratio of the atoms of different elements in a compound
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molecular formula
the numbers of atoms of different elements in one molecule of a compound
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Standard enthalpy change of reaction
The energy transferred when the molar quantities of reactants as stated in the equation react under standard conditions
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Standard enthalpy change of neutralisation
the enthalpy change when the amounts of acid and alkali in the equation for the reaction neutralise each other under standard conditions
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Standard enthalpy change of formation
the enthalpy change when one mole of the compound forms from its elements under standard conditions with the elements and compound in their standard (stable) states
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Standard enthalpy change of combustion
the enthalpy change when one mole of the substance burns completely in oxygen under standard conditions
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Standard enthalpy change of atomisation
the enthalpy change when one mole of gaseous atoms if formed from the element under standard conditionsr
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Hess' Law
The enthalpy change in converting reactants to products is the same regardless of the route taken, provided the initial and final conditions are the same
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Atomic Number
the number of protons in an atom's nucleus
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Mass number
the number of protons plus neutrons in an atom's nucleus
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Isotopes
atoms of the same element with the same atomic number, but different mass numbers
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Relative isotopic mass
the mass of one atom of an isotope relative to the mass of one atom of carbon-12 for which the relative mass is defined as exactly 12
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1st ionisation energy
the energy needed to remove one electron from each atom in one mole of gaseous atoms
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An orbital
A region in space around nucleus of an atom in which there's a 95% chance of finding an electron, or pair of electrons with opposite spins
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Electronic configurations
describe number and arrangement of electrons in an atom
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Lattice
A regular arrangement of atoms or ions in a crystal
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delocalised electrons
bonding electrons which are not fixed between two atoms in a bond. They are free to move
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Metallic bonding
The strong attraction between a lattice of positive metal ions and a sea of delocalised electrons
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electrolysis
The decomposition of a compound by electricity
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The first electron affinity
the energy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous ions with a single negative charge
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The lattice energy
the standard enthalpy change when one mol of compound forms from free gaseous ions
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Polarisation
The distortion of the electron cloud in a molecule or ion by a nearby charge
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Dative covalent bond
a bond in which two atoms share a pair of electrons, both the electrons having been donated by one atom
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Covalent bond
The electrostatic attraction between the two nuclei and the shared pair of electrons
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A functional group
group of atoms which gives an organic compound its characteristic properties
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Structural isomers
compounds with the same molecular formula but a different structural formula
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Free-radicals
Highly reactive, single atoms with unpaired electrons
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Nucleophiles
Ions with a lone pair of electrons that attack positive ions
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electrophiles
Reactive ions and molecules which attack negative ions
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Aliphatic hydrocarbons
Straight-chain and branched hydrocarbons with no rings of carbon atoms
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Alicyclic hydrocarbons
hydrocarbons with at least one ring of carbon atoms
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Arenes
Hydrocarbons with a ring of carbon atoms in which there are delocalised electrons
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A Substitution reaction
one in which an atom is replaced by another atom
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Initiation
the step which produces free radicals
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Propagation
The step which can form products and more free-radicals
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Termination
step which involves removal of free-radicals by turning them into molecules
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Sustainable lifestyle
living within the means of the environment in order that the earth's natural resources are available for future generations
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Cis-trans isomers (geometric isomers/stereoisomers)
Molecules with the same molecular formula, the same structural formula, but different displayed formula
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addition reaction
When two molecules add together to form a single product
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intermediates
atoms/molecules/ions/free-radicals which do not appear in the overall equation for a reaction but which are formed during one step of a reaction and used up in the next
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inductive effect
describes way in which electrons are either pushed towards or pulled away from a carbon atom by the atoms/groups to which it is bonded
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addition polymerisation
an addition reaction in which monomers join together to form a giant molecule
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Other cards in this set

Card 2

Front

Element

Back

the simplest chemicals- they cannot be broken down into simpler chemicals.

Card 3

Front

ion

Back

Preview of the front of card 3

Card 4

Front

molecule

Back

Preview of the front of card 4

Card 5

Front

compound

Back

Preview of the front of card 5
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