Atomic structure

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Atomic Structure
Development of the Molecule
Dalton ­ Elements are made up of invisible atoms, all atoms that make an element have a mass
Thompson ­ He discovered the electron and showed that they were negatively charged (plum pudding
Rutherford ­ Most of the positive charge was in a nucleus, discovered when alpha particles were fired at foil
Bohr ­ Electrons move around in shells and every atom has a specific number of shells
Chadwick ­ Found in neutrons in the atom of a nucleus
Modern Day Atom ­ Electrons move around in clouds and are not in a fixed position
Mass Number, Atomic Number and Isotopes
Mass No. ­ The number of protons and neutrons in the nucleus of an atom
Atomic No. ­ The number of protons in an element
Isotope ­ An element with the same number of protons and a different number or neutrons. This changes ...the mass
but does not change the chemical properties of an element
Time of Flight Mass Spectrometry
There are three main steps to this process which is used to find the relative atomic mass of an atom:
1. Ionisation
A sample is dissolved and injected through a fine needle into a vacuum
High voltage is applied which produces a positive charge
Solvent evaporates leaving 1+ ions
2. Separation of Charged Ions
Ions are accelerated using an electric field so they all have the same kinetic energy
Ion drift occurs when they enter the flight tube (lighter ions travel faster taking less time to reach the detector)
3. Detection
Negatively charged plate which produces a current when the positive ions hit the plate, the more ions the
bigger the current
Mass spectrum is used to display the results
(Abundance1x m/z + (Abundance
1) 2x m/z + (Abundance
2) 3x m/z3)

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Total Abundance
Electron Arrangement
S-Block ­ Outer Electrons are in the S sub-level (Group 1 and Group 2 are s-block)
P-Block ­ Outer Electrons are in the P sub-level (Group 3 ­ Group 7)
D-Block ­ Outer Electrons are in the D sub-level (Transition Methatls)
Ionisation Energy
First Ionisation Energy ­ The enthalpy change when an electron is removed from a gaseous ion to form
.....................................a uni-positive gaseous ion.
E.g.…read more

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Amount of Substance
Relative Atomic and Relative Molecular Mass
Atomic (Ar) ­ Average mass of an atom/element
mass of one atom of C12
Molecular (Mr) ­ Average mass of a molecule
mass of one atom of C12
Moles and Avogadro's Constant
A mole is the number of particles, the number of moles can be calculated by using the following
equation/triangle. This can also be used to calculate the mass (in grams) and the Mr of a compound.…read more

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Molecular Formula
This is the total number of atoms of each element in each molecule of a substance:
1. Take the empirical formula and Mr that is given
Mr: 78
2. Calculate the sum of the Mr
(12 + 1)n = 78
3.…read more

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Mass/Mr of all products
Ionic Equations
This takes an equation and writes it in terms of ions, for example:
CuSO4 (aq)+ 2NaOH (aq) Na
2SO 4 (aq)+ Ca(OH)2 (s)
1. Rewrite the equation with the ions. Solids cannot be written in terms of ions
2- + + 2-
Cu2+ + SO4 + 2Na + 2OH -
2Na + SO 4 + Cu(OH)2
2. Remove the ions that are the same from each side
+ 2OH- Cu(OH) 2
Percentage Error
Balances: + /-0.…read more


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