Revision notes on Bonding

aqa chemistry AS, nit 1, bonding. includes different types of bonding: ionic, covalent, dative covalent/coordinate, metallic; electronegativity and dipoles; shapes of molecules and bond angles; intermolecular forces: van der waals', permanent dipole-dipole attractions, hydrogen bonding; molecular crystals, macromolecular crystals, the structure of ice, states of matter.

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  • Created on: 25-11-12 19:03
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Bonding Notes
Between metals and non-metals.
Metal atoms lose electrons forming cations.
Non-metal atoms gain electrons and form anions.
Ions held together by strong electrostatic attraction forces forming a giant 3D lattice.
3D ionic lattice.
Face centred cubic lattice/ 6:6 lattice (for NaCl).
Physical Properties
High melting point- oppositely charged ions held together by strong electrostatic attraction forces.
Hard but brittle- lattice shatters under stress if planes of ions shift and therefore repel each other.
Soluble in polar solvents (water)- water reacts with ions and give enough hydration energy to break the lattice (lattice
Insoluble in non-polar solvents (hexane etc.)- non polar solvents can't interact with ions.
Conducts when molten/ in solution- Ions can't move when in a solid but become delocalised when in a solution or
molten and therefore act as an electrolyte and can carry a charge.
The electrostatic force of attraction that 2 neighbouring cations have for the delocalised electrons between them.
Only 1 type of metallic element.
Low electronic control- ability to lose outer electrons and form cations.
Bond strength varies depending on the metal- strongest bond when cations are small and charge on cation is large and
therefore number of delocalised is large.
A giant lattice- metal ions surrounded by delocalised electrons.
Physical Properties
High melting point (exception of mercury) - strong forces of electrostatic attraction between
cations and delocalised electrons.
Melting points decrease down a group- number of delocalised electrons and charge stay the same (same number of
electrons in outer shell) but size increases.
Melting points increase across a period- charge and number of delocalised electrons increases but size stays about the
Malleable and ductile- due to planes of ions sliding over each other.
Good electrical conductivity- delocalised electrons are free to move through the lattice, even when solid.
Metallic lustre- ability to reflect light.

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A shared pair of electrons.
Between 2 non-metals.
Both atoms want to gain electrons.
Coordinate/ Dative Covalent
A shared pair of electrons, just like in a covalent bond.
Both electrons originate from 1 atom in the bond.
One atom has a lone pair and acts as an electron pair donor (Lewis base); the other needs a pair and acts as an electron
pair acceptor (Lewis acid).
Once formed it acts like an ordinary covalent bond.…read more

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Intermolecular Forces
Forces between covalent molecules.
Three different types: Van der Waals', Permanent dipole-dipole, Hydrogen bonding from weakest to strongest.
Van der Waals' Forces
The weakest of the intermolecular forces.
Occurs in all species.
Electrons constantly move around inside their shells.
Electron distribution becomes asymmetric due to fluctuating movement of electrons.
This creates an instantaneous dipole in one molecule.
Dipole in one molecule repels electrons in the other and pushes them to the other
side of the molecule creating an induced dipole.…read more

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Molecular Crystals
A lattice of covalently bonded molecules held together by intermolecular forces.
Physical Properties
Molecular crystals held together by Van der Waals' forces are readily sublime (e.g. iodine
Electrical insulators- no charged particles free to move around the lattice.
Insoluble in water (I, S, P) - neutral molecules don't interact with polar water molecules.
Soluble in water- if they possess hydrogen bonding (ammonia, ethanol).
Soluble in non-polar solvents- e.g. hexane.
Can react with water (H2SO4, PCl5, P4O10)
Macromolecular Crystals
E.g.…read more

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Shapes of Molecules
How to determine the shape of a molecule:
Total number of electrons in outer shell of central atom.
Add 1 for each negative charge.
Subtract 1 for each positive charge.
Add 1 for each atom bonded to the central atom.
Divide by 2 to get the total number of electron pairs. The number of electron pairs tells you the basic shape of your
Count the number of atoms bonded to the central atom.…read more

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States of Matter
3 different states of matter.
High degree of order.
Particles vibrate around fixed positions.
When particles are heated they gain more kinetic energy and so vibrate more.
When particles have enough energy to overcome attractive forces the solid melts.
Energy is used in separating the particles and temperature stays constant.
Amount of energy required to melt solid depends on the type of bonding and structure.
Between the ordered solid state and the random gaseous state.…read more


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