Topic 3 - Covalent Compounds and Separation Techniques Flashcards
What is a covalent bond?
A shared pair of electrons between atoms
Why do atoms bond covalently?
To get a full outer shell
What is formed when atoms covalently bond with one or more other atoms?
A molecule
How is hydrogen, H2, bonded together?
-Covalently bond to share a pair of electrons so both have 2 in outer shell
-Form single covalent bonds
H–H
How is hydrogen chloride, HCl, bonded together?
-Atoms need one more electron for full outer shell
-Single covalent bond formed
H–Cl
How is methane, CH4, bonded together?
-Four covalent bonds
-Carbon needs 4 for full outer shell (half full)
-Hydrogen needs 1
H
I
H–C–H
I
H
How is oxygen, O2, bonded together?
- Oxygen has 6 outer electrons
- Sometimes form ionic bonds by taking 2 electrons
- Share 2 pairs of electrons
- Covalent bondO=O
How is water, H2O, bonded together?
-Covalent bonds
-Oxygen shares electrons w/ hydrogen
O
/ \
H H
How is carbon dioxide, CO2, bonded together?
-Covalent bond
-Double covalent bond
-2 pairs of electrons shared
O=C=O
What are the bonds like in a simple molecular covalent substance?
Very weak intermolecular forces
How strong is a covalent bond?
Very strong within the atoms of the molecule
What are the properties of a simple molecular covalent substance?
- Low melting + boiling points (molecules easily parted from each other as weak intermolecular forces)
- Most are gas/liquid at room temp.
- Don’t conduct electricity (no ions)
What is the difference between and ionic lattice and a giant molecular covalent substance?
No charged ions in giant molecular covalent substance
What type of bond is within a giant molecular covalent substance?
Strong covalent bonds
What are the properties of giant molecular covalent bonds?
- Very high melting + boiling points
- Don’t conduct electricity, even when molten (except graphite)
- Usually insoluble in water
What is the structure of a diamond atom?
- Made of carbon atoms
- Forms 4 covalent bonds
- Rigid giant covalent structure
What can diamond be used for?
Cutting tools (very hard)
What are the properties of diamond?
- Really hard (giant covalent structure)
- Doesn’t conduct electricity (no delocalised electrons)
What is the structure of graphite?
- Made of carbon atoms
- Has layers that can slide over each other
- Layers are held together loosely so can be rubbed off easily
- Each carbon atom forms 3 bonds (out of 4) so lots of delocalised electrons
What are the properties of graphite?
- Layers can easily slide over each other
- Layers can be rubbed off from one another
- Can conduct electricity (lots of delocalised electrons)
What can graphite be used for?
- Lubricant (layers slide over each other)
- Pencil (layers easily rubbed off from one another)
- Electrodes (lots of delocalised electrons so can conduct electricity)
What does miscible mean?
When 2 substances (liquids) mix together and don’t separate
What does immiscible mean?
When 2 substances (liquids) mix together but separate from one another back to original substance
How can you separate immiscible liquids from each other?
- Separating funnel
- 2 immiscible liquids shaken together + allowed to stand they separate into layers
- Denser liquid sinks to bottom + less dense on top
- Layers separated by separating funnel w/ tap
- Tap opened to drain denser liquid into beaker
- e.g. mixture of oil + water
