chemistry unit 1definitions

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  • Created by: charlie
  • Created on: 11-02-14 21:01
Avogadro constant
the number of atoms per mole of the carbon-12 isotope (6.02 x 10^23 mol^-1)
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mole
amount of any substance containing as many particles as there are carbon atoms in exactly 12g of C-12
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molar mass
mass per mole of a substance (gmol^-1)
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empirical formula
simplest whole number ratio of atoms of each element present in a compound
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molecular formula
actual number of atoms of each element in a molecule
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acid
species that is a proton donor
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base
species that is a proton acceptor
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alkali
type of base that dissolves in water forming hydroxide ions (OH-)
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relative isotopic mass
mass of an atom of an isotope compared with 1/12 of the mass of C-12
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relative atomic mass (Ar)
weighted mean mass of an atom of an element compared with 1/12 of the mass of C-12
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relative molecular mass (Mr) (covalent except Si02)
weighted mean mass of molecule compared to 1/12 of an atom of C-12 (add up R.A.M)
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relative formula mass (ionic)
weighted mean mass of a formula unit compared to 1/12 of an atom of C-12
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first ionisation energy
energy required to remove one electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous +1 ions
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Hund's rule
electrons occupy orbitals of same energy in singles before pairing up
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Pauli's rule
paired electrons must have opposite spin
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Ionic bonding
electrostatic attraction between oppositely charged ions (metal + non metal)
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covalent bonding
bond formed by a shared pair of electrons (non metal + non metal)
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metallic bonding
electrostatic attraction between positively charged ions and a mobil sea of delocalised electrons
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octet rule
when elements react they tend to acquire a stable noble gas configuration of electrons
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mixture
not chemically bonded and ratios aren't fixed
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compound
2 or more different elements chemically bonded
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exceptions to octet rule (less electrons)
Be + B small so can form stable molecules with less than 8 electrons
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exceptions to octet rule (more electrons)
P + S can make use of unoccupied higher energy orbitals to expand their octet
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lone pair reduces bonding angle by...
2.5 degrees
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non polar bonds
found between 2 identical atoms, 100% covalent, electron cloud uniformly spread,
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polar bonds
bonding atoms different, one with greater attraction for electrons is more electronegative, permanent dipole, uneven electron distribution cloud
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electronegativity
measure of attraction of a bonded atom for the pair of electrons in a covalent bond (F,O,N,Cl)
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polar molecules
one side slightly more electrons
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van der waals attraction
no polar bonds, temporary dipole - uneven electron distribution (constant movement), temporary dipole-dipole attraction,
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permanent dipole-dipole attraction
polar bonds, overall permanent attraction
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hydrogen bonding
permanent dipole-dipole attraction, H atom is bonded to very electronegative atom (F,O,N), strong attraction lone pair - exposed H nucleus
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dative/coordinate bond (lone pair not involved in chemical reaction)
covalent bond where one of 2 atoms provides both of the shared pairs of electrons
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isotope
atoms of the same element with different number of neutrons and different masses
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orbital
region of space when electron spend most of its time (holds 2 electrons with opposite spins)
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abundance
how much makes up an atoms + found by mass spectrometer
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ionisation energies
measure of how easily an atom loses an electron
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oxidation numbers
measure of the number of electrons that an atom uses to bond with atoms of another element.
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disproportionate reaction
redox reaction where element both oxidised and reduced at the same time
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OIL RIG
oxidation is loss (electrons), reduction is gain (electrons)
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Other cards in this set

Card 2

Front

amount of any substance containing as many particles as there are carbon atoms in exactly 12g of C-12

Back

mole

Card 3

Front

mass per mole of a substance (gmol^-1)

Back

Preview of the back of card 3

Card 4

Front

simplest whole number ratio of atoms of each element present in a compound

Back

Preview of the back of card 4

Card 5

Front

actual number of atoms of each element in a molecule

Back

Preview of the back of card 5
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