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36 Cards in this Set
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Relative atomic mass (Ar) /
Atomic weight / Average atomic mass |
average mass of an atom, taking into account relative abundances of all naturally occurring isotopes of the element, relative to one atom of C-12
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Relative molecular mass (Mr) /
Molecular weight / Average molecular mass |
equivalent to molar mass of a substance in grams
the average mass of a molecule calculated by adding the Ar of its constituent atoms |
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Mass number (A)
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sum of an atom's protons & neutrons
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Atomic number (Z)
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number of protons in atom's nucleus (determines identity of atom)
equal to the number of electrons it contains |
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Isotopes of an element
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atoms of the same element (same atomic number /Z) with a different number of neutrons (different mass number /A)
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First ionisation energy
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the minimum energy required to remove a mole of electrons from a mole of gaseous atoms to form a mole of univalent cations in the gaseous state
it is the enthalpy change for the reaction : X(g) → X^+ + e^- |
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Electronegativity
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measure of the tendancy of an atom in a moloecule to attract a shared pair of electrons towards itself
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Exothermic reaction
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Reaction that releases heat to surroundings
Enthalpy change = -ve Forms products with stronger bonds than the reactants |
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Endothermic reaction
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Reaction in which energy is absorbed from surroundings
Enthalpy change = +ve Forms products with weaker bonds than the reactants |
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Standard enthalpy change of reaction (delta H)
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the heat transferred during a reaction carried out under standard conditions:
temperature (298K) pressure (100 kPa or 1atm) all substances pure and in their standard state |
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Average bond enthalpy
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the energy required to break 1 mole of covalent bonds in the reactant, all reactants and products being in the gaseous state.
It is an average value because it takes into account the different energies in a bond between the same atoms in different molecules |
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Standard state
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standard state of an element is its most stable state under the specified conditions
A precisely defined reference state as: - Temperature of a substance at exactly 298K - Pressure of gaseous substance are exactly 1 atm - liquids & solids are pure - aqueous solutions are exactly 1 mol per dm cubed |
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Rate of reaction
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the increase in concentration of a reactant or product per unit time
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Activation energy (Ea)
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the minimum energy required for a chemical reaction to take place
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Bronsted-Lowry acid
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a proton donor
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Bronsted-Lowry base
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a proton acceptor
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Lewis acid
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electron-pair acceptor
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Lewis base
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electron-pair donor
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Oxidation
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loss of electrons
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Reduction
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gain of electrons
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Oxidising agent
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accepts electrons and becomes reduced
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Reducing agent
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donates electrons and becomes oxidised
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Solute
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the substance dissolved in a solvent forming a solution
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Solvent
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the liquid that dissolves another substance or substances to form a solution
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Solution
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a homogeneous mixture of a liquid (solvent) with another substance (solute)
there is usually some interaction between the solvent and solute molecules |
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Concentration
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the amount of solute in a known volume of solution
expressed as dm^-3 |
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Continuous Spectrum
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shows an unbroken sequence of frequencies
(eg. the spectrum of visible light) |
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Line Spectrum
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an emission spectrum that has only certain frequencies of light.
produced by excited atoms and ions as they fall back to a lower energy level |
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Group
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vertical column of elements in the Periodic table
the atoms of the elements in the same group all have the same outer shell structure but an increasing number of inner shells. |
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Period
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horizontal row of elements in the Periodic table
within a period the atoms of the elements have the same number of shells but with an increasing number of electrons in the outer shell |
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Strong acids and bases
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almost completely dissociated
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Weak acids and bases
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only partially dissociated
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Buffer
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A solution that maintains a relatively constant pH when small amounts of strong acid or strong base are added to it
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unsaturated
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containing at least one C=C double bond
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saturated
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containing no C=C double bonds
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nucleophile
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Reagents that have a non-bonding pair of electrons; attracted to the C atom in the halogenoalkanes during substitution reactions
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