3. Bonds

Question 1

Describe an ionic bond and a lattice of ionic compound

Answer 1

an ionic bond is a strong electrostatic
attraction between oppositely charged ions.

giant lattice structure of ionic compounds is a regular arrangement of alternating positive and negative ions held together by electrostatic force of attraction.

Question 2

Explain in terms of structure and bonding the properties of ionic compounds

Answer 2

high melting points and boiling points- strong electrostatic forces so a lot of energy is needed to separate ions and melt.

good electrical conductivity when aqueous or molten and poor when solid- mobile ions to move and carry charge.

soluble in water- water molecules bond with both + and - ions which breaks the lattice keeping ions apart.

Question 3

Covalent bond

Answer 3

a covalent bond is formed when a pair of electrons is shared between two atoms leading to noble gas electronic configurations

Question 4

Explain in terms of structure and bonding the properties of simple molecular compounds

Answer 4

low melting points and boiling points- weak intermolecular forces

poor electrical conductivity- no mobile ions

soluble in organic solvents only- non polar

Question 5

Define allotrophe

Answer 5

different atomic or molecular arrangements of the same element in the same physical state. ex- graphite and diamond of carbon

Question 6

Describe the giant covalent structures of graphite, diamond and silicon(IV) oxide, SiO2

Answer 6

G- within each layer, each carbon atom is bonded to three others by strong covalent bonds.

D- each of the carbon atoms is covalently bonded to four others forming a tetrahedron.

S- macromolecular compound which occurs naturally as sand and quartz. each O2 atom is covalently bonded to 2 Si atoms which bond with 4 O2 atoms forming a tetrahedron.

Question 7

Properties and uses of graphite and diamond

Answer 7

graphite as a lubricant, an electrode and in pencil- delocalised electrons bw layers. strong covalent bonds within layers so high MP and BP but weak forces bw layers so can slide over each other making it soft and slippery. a dark grey shiny solid.

diamond in cutting tools, jewellery- no delocalised electrons. hard- strong covalent bonds so high MP and BP. colourless transparent crystal which sparkles in light.

Question 8

metallic bonding

Answer 8

the electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

Question 9

Explain in terms of structure and bonding the properties of metals:

Answer 9

good electrical conductivity- delocalised electrons

malleability and ductility- layers of positive ions can slide over each other and take up different positions.

MP and BP- strong attraction so a lot of energy is needed to break the bond.

High density- atoms closely packed

Question 10

Describe malleable and ductile

Answer 10

M- can be hammered or bent into different shapes.

D- can be pulled into thin wires