Structure and Bonding

Question 1

describe covalent bonding

Answer 1

when atoms share electrons to create a molecule

Question 2

what is metallic bonding?

Answer 2

when metal atoms lose their outermost electron to form positively charged ions, the force of attraction between these delocalised electrons and positive metal ions

Question 3

describe the structure of ionic compounds

Answer 3

the oppositely charged ions are strongly attracted to each other, forming ionic bonds, which form a giant lattice structure with strong electrostatic forces of attraction

Question 4

what are the limitations of dot and cross, ball and stick, two and three dimentional diagrams to represent giant ionic structures?

Answer 4

• dot and cross- does not show how the atoms are arranged in space, that it is a 3D lattice structure of an ionic compound, that this is a giant compound
• three-dimensional ball and stick- using sticks for bonds is misleading because the forces of attraction between ions actually act in all directions
• two-dimensional- does not show how the next layer of ions is arranged
• three-dimensional- misleading because it shows lots of free space between the ions, which there isn’t

Question 5

how to draw a repeating unit of a polymer

Answer 5

1. change double bond to single bond
2. add bond to each end of repeat unit
3. draw brackets with the bonds going through
4. put letter n in bottom right

Question 6

how would you draw dot and cross diagrams for hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane?

Answer 6

• hydrogen, chlorine, oxygen, nitrogen- diatomic
• hydrogen chloride- H and Cl share one electron each (2 total)
• water- each hydrogen shares an electron, oxygen shares 2 (4 total shared)
• ammonia- NH3- nitrogen shares 3 electrons, each hydrogen shares one (6 total)
• methane- CH4- C shares 4, each hydrogen shares 1 (8 total)

Question 7

what 3-4 factors effect melting/ boiling point?

Answer 7

intermolecular forces, ionic bonds, shape and size of molecules

Question 8

describe the limitations of the particle model

Answer 8

• particles are not solid, since atoms are mostly empty space
• many particles are not spherical

Question 9

explain how the structure of ionic compounds effects their melting/ boiling points and conduction of electricity

Answer 9

• high melting/ boiling points because the ionic bonds (electrostatic attraction between the opposite charge) are very strong
• solid ionic compounds cannot conduct electricity, because those ions are held in place but they can when they are liquid or have been dissolved in water to form an aqueous solution because the charged particles (ions) are free to move

Question 10

how does the structure of small properties affect their properties?

Answer 10

• cannot conduct electricity- no overall electrical charge
• low melting/ boiling points- relatively little energy is needed to overcome their weak intermolecular forces

Question 11

how does the structure of polymers affect their properties?

Answer 11

• high melting/ boiling points- intermolecular forces between the larger polymer molecules are stronger, so more energy is needed to break them
• don’t conduct electricity- electrons are locked in their covalent bonds

Question 12

how does the structure of giant covalent structures affect their properties?

Answer 12

• high melting/ boiling points- lots of strong covalent bonds
• variable electrical conductivity- most substances with giant covalent structures have no charged particles that are free to move and can’t conduct electricity except graphite which does have free electrons

Question 13

how does the structure of metals and alloys affect their properties?

Answer 13

• alloys are harder and stronger than the pure metal because the different sized particles make them require a greater force for the layers to slide over eachother
• metals conduct electricity- delocalised electrons carry charge through the metal
• however in alloys- different atom sizes make their arrangement less regular, making the atoms weaker, giving them a lower melting point
• metals have high melting/ boiling points- strong metallic bonds
• however in alloys- the existence of impurities restricts the flow of electrons, so they have lower melting/ boiling points

Question 14

how does the structure of graphite, diamond and graphene link to their properties?

Answer 14

• graphite- conduct electricity (delocalised electrons), weak forces between layer= slippery/ used for lubricants, high melting point- strong covalent bonds between carbon atoms
• diamond- hard- rigid network of carbon atoms/ strong covalent bonds, high melting point- lots of strong covalent bonds, doesn’t conduct electricity
• graphene- conducts electricity- delocalised electrons, high melting point- strong covalent bonds, strong- strong covalent bonds

Question 15

draw the structure of fullerenes, state the uses of buckminsterfullerene and carbon nanotubes

Answer 15

• buckminsterfullerene- sphere made of hexagon and pentagon shapes of bonds (circle in each corner= carbon atoms)
• used as lubricants and are starting to be used in many industrial processes due to their spherical shape and lack of bonding forces between them
• nanotubes- cylinder with no ends made of hexagon shapes of bonds (circle in each corner= carbon atoms)
• they are strong and conduct electricity so are useful for nanotechnology, electronics and specialised materials