Covalent Bonding
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Define covalent bond
Strong electrostatic attraction between the bonding electron pair and the positive nucleus (Atoms share electrons)
What do we call the elements in group 7 of the periodic table?
The halogens
How many outer shell electrons do halogen atoms have?
7
Are covalent bonds formed between metals or non metals?
Non metals
There are 2 types of molecular substances that have covalent bonding? What are they?
Simple molecular substances Giant molecular substances
What type of bonding takes place between a metal and non metal?
Ionic bonding
What are the 3 allotropes (different forms) of carbon?
Diamond Graphite Buckminster fullerine (Carbon 60 fullerine)
Covalent compounds do not usually conduct electricity. Why?
No delocalised electrons
Properties of diamond
Giant molecule made from 4 strong covalent bonds Does not conduct electricity Extremely hard Very high melting and boiling points used for cutting tools
Properties of graphite
Giant structure made up of 3 bonds Weak intermolecular forces between layers Conducts electricity Soft and slippery High melting and boiling points
Properties of buckminster fullerene
Simple molecular structure Lower melting and boiling points Does not conduct electricity Soft and slippery Used as a lubricant
Simple Molecular Substances have very low melting and boiling points. Why?
Weak intermolecular forces of attraction between molecules Needs less energy to separate molecules
The bigger the mass of the molecules, the higher the melting and boiling points get. Why?
Bigger masses have bigger intermolecular forces More energy needed to separate molecules
Giant Molecular Substances have very high melting and boiling points. Why?
All atoms joined by strong covalent bonds Lots of energy needed to separate atoms
Examples of Giant Molecular Substances are …
Diamond, graphite, silicon dioxide (sand)
Examples of Simple Molecular Substances are …
Hydrogen, chlorine, ammonia, buckminster fullerine