Atomic Structure

AS atomic structure revision cards, based on the information that needs to be covered on the specification for the AQA exam board.

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  • Created by: Jas
  • Created on: 29-10-11 16:34

Fundamental Particles.


relative mass = 1

relative charge = +1


relative mass = 1/1836

relative charge = -1


relative mass = 1

relative charge = 0

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Relative Atomic Mass(Ar) and Molecular Mass (Mr)

Relative Atomic Mass.

The mass of an atom relative to the carbon-12 atom having a value of 12.00.

Ar =  (average mass per atom of element x 12) ÷ (mass of one atom of carbon-12)

Relative Molecular Mass.

Instead of the mass of a carbon-12 atom, uses the mass of the molecule.

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Mass Number and Atomic Number


Mass number = Protons and Neutrons

Atomic Number = Electrons (Which is equal to amount of protons)

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The same number of protons, but a different number of neutrons.

CHEMICAL properties are the same, but DENSITY and MASS will change

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Mass Spectrometry

IONISATION = gaseous atoms fired with electrons form electron gun and are ionised. Sufficient energy is given to form ions with +1 charge. 

ACCELERATION = the ions can then be accelerated out by an electric field, any neutral molecules that aren't ionised due to fragmentation wont be affected since they are uncharged and not accelerated.

DEFLECTION = charged particles are deflected by a magnetic or electric field, the path of the ion depends on mass/charge ration (m/z). Large m/z ratios have larger radius curves, smaller m/z ratios have smaller radius curves.

DETECTION = Mass spectra records the m/z value and the relative abundance of all fragments. Data found provides exact molecular masses of molecules.

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Electron Configurations

4 Shells each with different orbitals, each orbital can contain 2 electrons.

S = 1 (2 electrons) P = 2 (4 electrons) D= 5 (10 electrons) F = 7 (14 electrons)


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Ionisation Energy

1st ionisation energy = the energy required to remove one electron from each atom in 1 mole of gaseous atoms producing 1 mole of gaseous atoms. 


2nd ionisation energy = energy needed to remove the second electron ALONE, not both electrons. 

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Factors affecting ionisation energy.


The more protons in a nucleus, the more positively charged the nucleus increasing the attraction of the electrons.


The further away the electron is from the nucleus, the easier the ionisation will be as the attraction is a lot smaller. 


The more electrons between the nucleus and the outer electron shields the outer electron from the attraction of the nucleus making it easier to lose the outermost electron.

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Ionisation Patterns in Period 3


Electrons are going into the same 3-level shell with the same shielding. The only change is the number of protons which is increasing, therefore increasing the attraction towards the nucleus so the IE gradually increases. 

The Fall at Aluminium....

Al's outer electron is in 3p which is slightly further away from the nucleus than 3s. This means that the pull from the nucleus is slightly less as it is further away and also the electron is shielded slightly by the electrons in 3s.

The Fall at Sulphur ...

The electrons don't pair up in 3p until sulphur. Because the first set of electrons in Sulphur have paired up, the repulsion between the two electrons make it easier for the electron to be lost - hence the slightly lessened IE needed. 

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Ionisation Patterns in Group 2


This is due to shielding, because as you go down the group the number of electrons between the nucleus and the outermost electron gets bigger therefore reducing the attraction of the nucleus and making it easier to lose an electron. 

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Mass Spec = Finding Relative Isotopic Mass and Rel

Relative Isotopic Mass

Because most of the ions formed will have a +1 charge, the m/z ration will simply be the Relative Isotopic Mass.

Relative Abundance

To find with out you have to take each 'line' which represents the isotopes and find the isotopic mass. Then multiply each isotope by its abundance and isotopic mass, then divide all of that by the combined isotopic masses.

Eg, Boron-10(abundance 23) and Boron-11(abundance 100)

(10x23) + (11x100) = 1330

1330÷123 = 10.8

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