Covalent Bonding Flashcards
(28 cards)
3 properties of simple covalent molecules:
> Many are gases
Low melting and boiling points
Do not conduct electricity
Why do covalent bonds have Low melting and boiling points?
> This is because there are weak forces between molecules —– Intermolecular forces
Little energy required to break them
Why do covalent bonds not conduct electricity?
> No free charges (delocalised) to carry charge throughout structure
What is a covalent bond?
A chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding.
How strong is a covalent bond?
Strong
How strong are intermolecular bonds?
Weak
Which bonds are broken when substance made of covalent molecules is broken?
Intermolecular bonds
Uses for covalent bonds-
> Fuels (e.g. CH4)
What type of elements make up covalent molecules?
non-metals
Chemical structure of Silicon Dioxide (SiO2)
> Tetrahedral structure of covalent bonds
Si - 4 bonds - O
O - 2 bonds - Si
Does SiO2 conduct electricity
No > no free electrons
Chemical structure of Diamond
> Tetrahedral structure of covalent bonds
Very strong
Each C bonds to 4 others
C-C bonds very strong
Physical properties of Diamond
> Good thermal conductor
Does not conduct electricity (no delocalised electrons)
High melting and boiling points
lots of strong covalent bonds - lots of energy to break
Chemical structure of Graphite
> Hexagonal > Each C 3 bonds to other carbons remaining > 4th electron is delocalised > 1 atom thick layers > weak forces in between layers
Can Graphite conduct electricity?
Yes.
4th electron delocalised, when voltage applied can be used as electrode
Giant covalent lattices’ intermolecular forces…
DONT EXIST!!
Uses of Graphite:
> Lubricant because layers can slide over each other
Physical properties of Graphite:
> Can conduct electricity
High melting and boiling points (sublimes at 3600º)
lots of strong covalent bonds, lots of energy to break
Polymers >
These are long molecules of small repeating units
Two types of polymers
> Thermo plastics - can be reshaped by heating
> Thermosetting plastics - cannot be reshaped by heating
What are cross links?
They join the chains in thermosetting plastics to make it rigid
What are diamond and graphite in relation to Carbon?
2 of its allotropes
What is Graphene?
A single layer of graphite (1 atom thick)
Properties of Graphene
> very good conductor of electricity
very strong
flexible
