4.2 COVALENT BONDING
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Define Covalent Bonding
The strong electrostatic force of attraction between a shared pair of electrons and positively charged nuclei of bonding atoms
How do you draw dot and cross covalent diagrams
• Find out how many electrons each atom has in its outer shell • Draw them next to each other sharing electrons in pairs • It can be more than one bond per atom • Each atom should have a full outer shell with any excess electrons being drawn in pairs
How do you draw a stick diagrm
• Draw the symbol of the atom and however many bonds draw with a line (a double bond with have 2 lines ect.) • Draw them up like the dot and cross diagram
What are the bonds between molecules in simple molecular substances
Intermolecular forces
What are the bond within molecules
Strong Intramolecular covalent bonds
Why does the boiling point increase in molecules a larger mass number
• As the molecular mass increases, so does the strength of the weak intermolecular forces • So the boiling point increases as more energy is needed to overcome the weak intermolecular forces as these forces are greater
Why don’t simple molecular substances nerver conduct electricity
The molecules are always neutral
How many carbon atoms in a ball of Buckminster fullerene
60
Why is the boiling point of buckminster fullerene low but not as low as other simple molecules
It has a high molecular mass
Why is buckminster fullerene a soft and slippery solid
The molecules can roll over each other easily due to the weak intermolecular forces between the molecules
Why is buckminster fullerene an electrical insulator
The molecules are neutral and there are no delocalised electrons free to move around the structure
What is a allotrope
An all carbon substance
How is diamond arranged
• Giant lattice • Tetrahedral • Strong grid like arrangement • Every carbon atom makes 4 strong intramolecular covalent bonds • Very strong and hard
Why does diamond sublime/melt/boil at a very high temperature
• Diamond is a giant covalent structure • The intramolecular covalent bonds are very strong • There are lots of strong intramolecular covalent bonds in the giant covalent lattice • Lots of energy is required to break all the strong intramolecular covalent bonds
What is the hardest substance
Diamond
What are the uses of diamond
Cutting, engraving and drills
Why can’t diamond conduct electricity
• There are no freely-moving delocalised charged electrons free to move around the structure • All the atoms are neutral, and all the electrons are stuck inside an atom or a bond due to all 4 of carbon’s outer shell electrons being bonded • So charge cannot flow through the structure and so no electricity can flow
Is graphite a pure form of carbon
Yes
How is graphite arranged
• A giant lattice of layers connected by weaker intermolecular forces between the layers • Layers of hexagons of carbon atoms • Every carbon atom makes 3 strong intramolecular covalent bonds with other atoms • This leaves delocalised electrons inside each layer
Why does graphite sublime/melt/boil at a very high temperature
• Graphite is a giant covalent structure • The intramolecular covalent bonds are very strong • There are lots of strong intramolecular covalent bonds in the giant lattice • Lots of energy is required to break all the strong intramolecular covalent bonds
Why is graphite used as a solid lubricant
It is soft and slippery because the layers can slide easily.
Why can graphite conduct electricity
• In the giant covalent structure, 3 out of the 4 outer shell electrons from the carbon atoms make bonds with other atoms • This leaves 1 electron delocalised and free to. ove around the structure • Therefore charge can flow through these electrons, hence allowing electricity to flow
Is silicon dioxide an allotrope
No - No carbon
What is the structure of silicon dioxide
• Every silicon atom makes 4 covalent bonds • Every oxygen atom makes 2 covalent bonds • It is a tetrahedral shape • Strong grid like arrangement