covalent bonding

Question 1

covalent substances with simple molecular structures have _____ melting and boiling points

Answer 1

low mp and bp:
- they have simple molecular structure with weak intermolecular forces of attraction between molecules
- little energy is needed to overcomes these forces

Question 2

covalent substances with simple molecular structures are ________ in water and _______ in organic solvents ( not water )

Answer 2

insoluble in water and soluble in organic solvents
exceptions: alcohol/ sugar/ CO2/ HCL/ SO2/ NO2? NH3/ CL2/ BR2/ I2 are soluble in water

Question 3

covalent substances with simple molecular structures _____ conduct electricity in ____

Answer 3

they exist in molecules, hence there are no mobile ions or electrons to carry charges

exceptions:
- hydrogen chloride, carbon dioxide and ammonia form ions when dissolved in water
- these ions are mobile and can carry charges

Question 4

diamond and graphite are allotropes of carbon
what is the definition of allotropes

Answer 4

allotropes are different forms of the same element with different arrangement of atoms

Question 5

bonding of diamond

Answer 5

each carbon atom is bonded to 4 other carbon atoms by strong covalent bonds in tetrahedral arrangement

Question 6

bonding of graphite

Answer 6

earth carbon atom is bonded to 3 other carbon atoms by strong covalent bonds in a layer of hexagonal rings
each layer of carbon are held together by weak forces of attraction

Question 7

bonding of silicon dioxide

Answer 7

each silicon dioxide is bonded to 4 oxygen atoms and each oxygen atom is bonded to 2 silicon atoms by strong covalent bonds

Question 8

diamond have ____ mp and bp

Answer 8

• they have giant molecular structures with strong covalent bonds between the carbon atoms that extent throughout the structure to form a giant network of bonds
• a lot of energy is needed to break those bonds

Question 9

diamond is

Answer 9

hard and strong
- used in tips of drilling tools due to the giant network of strong covalent bonds between each carbon atoms which extends throughout the structure which requires a lot of energy to break

Question 10

diamond’s electricity conductivity

Answer 10

cannot conduct electricity in all states
- all valance electrons are used for bonding
- no mobile ions or electrons or carry electrical charges

Question 11

graphites have ____ mp bp

Answer 11

high
- they have giant molecular structures with strong covalent bonds between the carbon atom h\that extent throughout the structure to form giant network of bonds
- a lot of energy is needed to break those bonds

Question 12

graphites are

Answer 12

soft and slippery
- used as dry lubricants due to weald forces of attraction between layers of carbon atoms
- little energy is needed to overcome these forces of attraction
- layers of carbon atoms can slide past one another easily when a force is applied

Question 13

electrical conductivity of graphite

Answer 13

• each carbon atom is bonded to 3 other carbon atoms, leaving behind one mobile electron per carbon atom to carry charges
• there are mobile ions or electrons to carry the electrical charges