chemistry definitions

atomic number
the number of protons in the nucleus
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mass number
the number of protons and the number of neutrons in the nucleus
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atoms of the same elements having the same number of protons but different numbers of neutrons
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first ionization energy
the enthalpy change in forming 1 mole of gaseous 1+ ions from a mole of gaseous atom X(g) --> X+ + e
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relative atomic mass
(average mass per atom of an element x 12) / mass of one atom of carbon 12
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relative formula mass
(average mass of a molecule X 12) / mass of one particle per mole
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avogadro's number
the number of particles per mole
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the amount of substance containing the same number of particles as there are atoms in 12.00g of carbon 12
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empirical formula
the simplest ratio of atoms of each element in a compound
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molecular formula
the actual number of atoms of each element in a compound
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% atom economy
(mass of desired product / total mass of reactants) x 100
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% yield
(actual yield/theoretical yield) x100
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the power of an atom to withdraw an electron density fro a covalent bond
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structural isomerism
molecules having the same molecular formula but different arrangements in space
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homologous series
group of chemicals having : 1- the same general formula 2- same functional group 3- same chemical properties
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functional group
atom or group of atoms in a molecule that is responsible for the chemical properties of this molecule
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containing only c-c single bonds
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containing one or more C=C bond
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containing hydrogen and carbon only
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a process that converts large hydrocarbons into smaller ones by breaking C-C bonds
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complete combustion
reaction in excess oxygen
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incomplete combustion
reaction with restricted supply of oxygen so that some products have the potential to react further with oxygen
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green house gas
a gas in the atmosphere that absorbs infra red radiation reflected form the earth
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global warming
he warming of the atmosphere as a result of greenhouse gases absorbing reflected radiation
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covalent bond
shared pair of electrons
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co-ordinate bond
covalent bond (shared pair of electrons) where both electrons are from one atom
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ionic bond
electrostatic attraction between oppositely charged ions
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metallic bond
attraction between positive metal cations and a sea of delocalised electrons
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polar bond
a covalent bond with an unequal share of electrons between the atom so that it has d+ and d-
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polar molecule (dipole)
a molecule with d+ and d-
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intermolecular force
a force of attraction between neighbouring molecules
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dipole dipole force
attraction between two polar molecules
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enthalpy of formation
the enthalpy change when one mole of a compound is formed from its elements in their standard state
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enthalpy of combustion
the enthalpy change when one mole of substance is completely combusted under standard conditions
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hess's law
if a reaction can occur by more than one route, the overall enthalpy change is independent on the route taken
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Card 2


mass number


the number of protons and the number of neutrons in the nucleus

Card 3




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Card 4


first ionization energy


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Card 5


relative atomic mass


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