chem bonding: bonding and structure

Question 1

propoerties of simple covalent structures?

Answer 1

• simple covalent molecules are usually gas or liquids at rtp
• strong intramolecular forces between atoms
• weak intermolecular forces between molecules

Question 2

properties of giant covalent structure?

Answer 2

• giant covalent molecules are usually solids at rtp

- all atoms are bonded togethr by strong covalent bonds

Question 3

bonding of diamond?

Answer 3

each C atom is covalently bonded to 4 other C atoms in a tetrahedral arrangement

Question 4

bonding of silicon dioxide?

Answer 4

each Si atom is covalently bonded to 4 O atoms and each O atom is bonded to 2 Si atoms

Question 5

bonding in graphite?

Answer 5

each C atom is covalently bonded to 3 other C atoms in a hexagonal ring, and layers are held together by weak id-id attractions

Question 6

why do simple covalent molecules have low mp and bp (<200)?

Answer 6

low amount of energy is required to overcome the weak intermolecular forces between the simple discrete molecules

Question 7

why can’t simple covalent molecules conduct electricity?

Answer 7

this is because there is an absence of mobile carriers (ions/electrons)

Question 8

why are simple covalent structures generally insoluble in H2O and polar solvents but soluble in non-polar (organic) solvents?

Answer 8

most simple covalent molecules can only firm weak intermolecular forces with water and there is insufficient energy released to compensate for the energy needed to break up the stronger hydrogen bonds between H2O molecules, they are only soluble in water if they are able to form hydrogen bonds with water