CHE - Metallic Bonding

Question 1

What are the properties of metallic bonding?

Answer 1

1. Conduct electricity
2. Conduct heat
3. Malleable and Ductile
4. High boiling/melting points
5. Lustrous

Question 2

Why do metals conduct electricity?

Answer 2

Sea of delocalised electrons free to carry electric charge, as they move away from neg and towards pos electrode

Question 3

Why are metals malleable and ductile?

Answer 3

When cations move past each other, layers of ions will still be held together by sea of delocalised electrons between them, as they move too

Question 4

Why do metals have high boiling/melting points?

Answer 4

Strong electrostatic attraction between cations and electrons (sea)

Question 5

Why are metals lustrous?

Answer 5

Electrons fill the space between cations, making it tightly packed and dense and smooth surface > shiny and lustrous

Question 6

Why do metals conduct heat?

Answer 6

Sea of delocalised electrons bump into each other and cations, heating > rapid vibrations > transmit throughout as free to move

Question 7

What does the metallic bonding model not explain?

Answer 7

Range of melting temps and densities, differences in electric conduction, magnetic nature of Co, Fe, Ni

Question 8

What are the properties of transition metals and why?

Answer 8

• D-block (partially or fully filled d subshell next to be filled)
• Have s2 in outermost shell (for stability, cause of similar properties)
• Hard, high melting/boiling temps (bonds are stronger b/c greater core charge > packed and dense)
• Each ion surrounded by ~ 12 others
• Different coloured compounds/solutions (b/c of varying oxidation states b/c of d-orbitals - 3d & 4s have similar energy, electrons in both or only outer can be lost to form ions
• Complexes (weak co-ordinate bonds to ligands, b/c higher charge:size ratio
• Effective catalysts (d-subshell take/lend electrons easily, good for redox)

Question 9

What are alloys?

Answer 9

Mix of multiple metals or metal + carbon, melted > mixed > cooled
Make metal’s properties more efficient/advanced (improve on pure form)
Harder, less malleable and poorer electrical conductors

Question 10

What are the two types of alloys?

Answer 10

1. Substitutional : similar chemical property and sized metals, strong but harder and less malleable (eg. 75% Cu 25% Ni)
2. Interstitial: small proportion of metal w/ really smaller atoms (eg C + Fe = steel > harder and less malleable again

Question 11

Name some examples of alloys.

Answer 11

Bronze = 90% Cu and 10% Sn
Brass = 65% Cu and 35% Zn
Steel = Fe and C

Question 12

What are the properties of smaller crystals?

Answer 12

Harder (less free movement of layers of ions over each other
Brittle (more areas of disruption between crystals

Question 13

Describe the two ways of altering crystal structure.

Answer 13

1. Work hardening: hammer or work cold metals > rearrangement of crystal grains > harder / stiff / more brittle
2. Heat treatment: annealing (heating metal to medium temp > cool slowly > larger crystals form > soft and ductile), or quenching (heat to medium temp > cool quickly > tiny crystals form > hard and brittle) or tempering (quenched metals warmed again to lower temp > less brittleness but retain hardness > intermediate sized crystals