Chemistry Module 1 Unit 1 AS AQA

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  • Created on: 30-12-12 18:22
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Ionisation energies ­ The first ionisation energy of an element is the energy required to
remove one electron from each atom in one mole of gaseous atoms to form one mole of
gaseous 1+ ions.
As you go down the group the first ionisation energy decreases despite the increasing nucleus
charge. This is because there is a larger distance between the electron and nucleus and there are
more shells therefore more shielding.
As you go across the period, the first ionisation energy increases. This is because the distance
and number of shells between the electron and the nucleus whilst the nuclear charge increases.
An orbital is a region within an atom that can hold up to 2 electrons with opposite spins.
An S-orbital is spherical in shape. There is one S-orbital.
An P-orbital is dumb-bell in shape. There are three P-orbital.
The order is: 1s2 2s2 2p6 3s3 3p6 4s2 3d10 4p6
4s is filled before 3d, but electrons are removed from 4s because when it is full it has a higher
energy level.
Ionic bonding
Occurs between metals and non-metals.
Metals lose electrons in order to get a full outer shell.
The non-metals gain these electrons to get a full outer shell and their opposite charges
attract each other creating strong ionic bonds.
Metals have positive charges, the non-metals have negative charges.
Ionic compounds will not conduct electricity when solid, but will when molten or
aqueous as the ions are free to move around.
Metallic bonding
Occurs between metals.
Outer shell electrons in metal atoms are delocalised and are free to move around.
These electrons are shared between all the atoms and the electrostatic force between
the ions and electrons are very strong.
Electrical conductivity in a metal, the electrons are free to flow between the positive
ions.
Positive ions do not move.

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Covalent bonding
Occurs between non-metals.
It involves the sharing of electrons between the atoms in the compound in order to gain
a full outer shell (pair of shared electrons).
Simple covalent
o Strong covalent bond and weak forces between molecules, therefore low
melting and boiling points.…read more

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As you go along a period the electro negativity increases as nuclear charge increases. As you go
down the group, the electro negativity decreases as there are more shells which shield the
nucleus from electrons (more shielding).
Electro negativity and bonding type
Two different elements with a small difference in electro negativity
o The more electronegative atom will have more bonded electrons.
o The result is a polar covalent bond.…read more

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Dipole-dipole interaction between a positive atom of one molecule and a negative atom of
another molecule.
An intermolecular ­ attractive force between neighbouring molecules.
A permanent dipole-dipole force ­ weak attractive force between permanent dipoles in
neighbouring polar molecules.
Van der Waals' forces ­ attractive forces between induced dipoles in neighbouring molecules.
Van der Waals' forces exist between all molecules, whether polar or non-polar. Van der Waals'
forces are weak intermolecular attractions between very small, temporary dipoles in
neighbouring molecules.…read more

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