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Atomic structure Amount of substance
Isotopes: atoms with the same number of protons but A mole of a substance is the amount of that substance
different numbers of neutrons that contains the same number of particles as there are
Relative isotopic mass: the ratio of the mass of one atom carbon atoms in 12.00000 grams of carbon-12.
of that isotope to 1/12th of the mass of one atom of Avogadro's constant is 6x1023
carbon-12 PV = nRT P in Pascals, V in m3, T in Kelvin, n in moles
Relative atomic mass: the average mass of an atom to Mol = mass/Mr
1/12th of the mass of one atom of carbon-12 taking into Concentration = mol/volume (vol in dm3 ) m3 to dm3
account the abundances of its isotopes. divide by 1000
Relative molecular mass: the average mass of a molecule % Atom economy = (mass of desired product/mass of
relative to 1/12th mass of carbon-12 reactants) x 100%
% Yield = (mol of product/theoretical mol of product) x
Mass Spectrometry Calculations
Vaporised sample released into ionization chamber. Empirical Formula when given the mass or percentages,
Particles bombarded with electrons and ionized, mostly divide that by the Mr to get the number of moles. And
to +1 ions (IONISATION) divide through by the smallest number of moles. Do the
Ions accelerated to uniform speed by electric field same for water of crystallisation.
(ACCELERATION). The positive ions are attracted to the Molecular formula given the mass of each molecule,
negative plate and accelerate towards it find the number of moles by dividing the mass by the Mr
Ions deflected by magnetic field; deflection depends on and find the simplest whole number ratio of the moles.
m/e ratio (DEFLECTION) The heavier the particle, the less Titration to find the concentration of the unknown: write
the deflection a balanced equation, work out mol of neutraliser, apply
Electric current measured as ions land on plate to mol of unknown and use formula to find
Mass Spec Graph Bonding - Ionic
The magnitude of the peak gives the relative abundance Ionic bond - attraction between oppositely charged ions,
of the isotope. which are formed by the transfer of electrons from the
Thus the relative atomic mass of the element can be metal to the non-metal so that both atoms have full
calculated from its mass spectrum. outer shells.
The relative atomic mass can be calculated by the Ionic compounds form a lattice. All the cations are
formula: surrounded by anions and vice versa so that the repulsive
(% abundance of each isotope x mass of each forces are balanced.
isotope)/100 Ionic compounds are solid at room temperature and
It is also possible to put molecules into the mass have giant structures and therefore high melting points as
spectrometer. The molecules often break up into smaller energy is needed to break the attraction in the lattice.
pieces. This is known as fragmentation. They conduct electricity when molten as the ions are free
The relative molecular mass of a molecule is obtained by to move around and generate a current.
looking at the peak in the spectrum with the largest m/e They are brittle as a blow may cause like ions to come
ratio called the molecular ion peak. into contact.
Electron configuration Bonding Covalent
Electrons occupy certain fixed energy levels s, p, d and f Covalent bonding the sharing of electrons between two
shells. Any atomic orbital can hold a max of 2 electrons non-metals e.g. diatomic molecules.
in opposite spin. S has 2, p has 4 and d has 10 at their These molecules have low melting points as the strong
max. covalent bonds are only between the atoms of the
The arrow and box method represents each orbital as a molecules. There is weak attraction between the
box and each electron as an arrow. The direction of spin molecules so not much energy is required to break them.
is shown by the orientation of the arrow. Co-ordinate bonding/ dative bonding is when one atom
Many of these sub-levels have similar energy, and can be provides both the electrons being shared. This is usually
grouped together. A collection of sub-levels of similar because the donator has a lone pair. This is represented
energy is called a shell. by an arrow E.g. the ammonium ion. When NH3 reacts
1s2s 2p3s 3p 4s 3d 4p 5s 4d 5p6s 4f with H+ it becomes NH4+
Ionisation energies Bonding Metallic
First ionisation energy: the energy required to remove Metals consist of a lattice of cations surrounded by a sea
one electron from one mole of gaseous atoms to form of delocalised electrons. They have giant structures as
one mole of singly charged cations. X(g) X+(g) + e- the cations are spread out.
Second ionisation energy: the energy required to remove They are good conductors of electricity as the electrons
one electron from each of a mole of singly charged are delocalised and also good thermal conductors as the
gaseous cations to form one mole of doubly charged electrons gain kinetic energy.
cations. It is always endothermic as energy is required to
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The strength of metals depends on the charge on the ion
nucleus X+(g) X2+(g) + e- (greater electrostatic forces) and the size of the ion
(smaller, electrons closer to nucleus). They are malleable
and ductile and have high boiling/melting points due to
attraction of electrons and cations.
Trends in IE Intermolecular Forces
Across period 3 is a general increase as the nuclear Van der Waals attraction of electrons and nucleus form
charge increases and the shielding remains the same. very small electrostatic forces.…read more
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In industry there is more demand for shorter chained NOx produced in car engines, at high temps, or sparks
hydrocarbons so longer chains are broken down to occur. They react with O2 in the air to make nitric acid
produce useful materials e.g. petrol, polymers, drugs and causing smog.