The Metallic Model

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Metallic Bonding

Metal atoms are tightly packed in lattice structures.
Outer shell electrons become delocalised and are free to move throughout the structure.
Metal atoms become positively charged when they lose their outer electrons.
The positive charges repel each other, keeping the neatly arranged lattice in place.
There are very strong electrostatic forces between the positive metal centres and the 'sea' of delocalised electrons.

Metallic bonding and malleability

Properties of Metals: Malleability and Ductility

Metals are malleable (can be hammered into sheets) and ductile (can be drawn into wires).
The layers of metal ions can slide over each other when a force is applied.
The delocalised electrons allow the metal to retain its structure without breaking the bonds.

Malleability of metals

Properties of Metals: Strength and Hardness

Metals are typically strong and hard.
This is due to the strong electrostatic attraction between cations and electrons.
The closely packed structure of the metal ions also contributes to strength and hardness.

Properties of Metals: Electrical Conductivity

Metals conduct electricity in both the solid and liquid states.
Mobile delocalised electrons can freely move and conduct electricity.
When a potential difference is applied, delocalised electrons repel away from the negative terminal and move towards the positive terminal.
As the number of outer electrons increases across a period, the number of delocalised charges also increases: Na = 1, Mg = 2, Al = 3.
Therefore, the ability to conduct electricity increases across a period.

Properties of Metals: Thermal Conductivity

Metals are good thermal conductors due to the behaviour of their cations and delocalised electrons.
When heated, cations vibrate more vigorously and transfer kinetic energy as they collide with neighbouring cations.
Delocalised electrons are free to move and carry increased kinetic energy rapidly throughout the metal.

Properties of Metals: Melting and Boiling Points

Metals have high melting and boiling points.
This is due to the strong electrostatic forces of attraction between the cations and delocalised electrons in the metallic lattice.
These forces require large amounts of energy to overcome.
As the number of mobile charges increases across a period, melting and boiling points increase due to stronger electrostatic forces.

Uses of Metals

The metal chosen for a particular job depends on properties such as malleability/ductility, melting/boiling point, density, reactivity, electrical conductivity, strength, toxicity, lustre, thermal conductivity, strength-to-weight ratio, corrosion resistance, and sonority.
Aluminium is used in food cans because it is non-toxic and resistant to corrosion and acidic food stuffs.
Copper is used in electrical wiring because it is a good electrical conductor and malleable/ductile.
Stainless steel is used for cutlery as it is strong and resistant to corrosion.

Factors Affecting the Strength of Metallic Bonds

The charge on the metal ion: greater charge means more delocalised electrons and a greater charge difference between ions and electrons, leading to stronger electrostatic attraction.
The radius of the metal ion: smaller ionic radii exert a greater attraction on the sea of delocalised electrons, meaning a stronger metallic bond.
The strength of electrostatic attraction can be increased by: increasing the number of delocalised electrons per metal atom, increasing the number of positive charges on the metal centres, and decreasing the size of the metal ions.

Trends in Melting Points of Metals

Across a period (e.g., Na, Mg, Al): the charge on the metal ion increases and the ionic radius decreases, leading to stronger metallic bonding and higher melting points.
Melting point data for Period 3 metals: Na = 371 K, Mg = 922 K, Al = 933 K.
Down a group (e.g., Group 1): the size of the cation increases, which decreases the attraction between the outer electrons and the metallic lattice, so melting point decreases.
Melting point data for Group 1 metals: Na = 371 K, K = 337 K, Rb = 312 K.
The stronger the metallic bonding, the more energy is needed to break the metallic lattice, so the higher the melting point.
These are trends, not rules; other factors such as metal packing structure can cause subtle differences (e.g., Al melting point is not much higher than Mg).

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Practice questions

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1.Which of the following types of bonds does the statement 'electrostatic attraction between cations and delocalised electrons' best describe?
Easy
- Ahydrogen
- Bionic
- Cdipole-dipole
- Dmetallic
2.Which of the following materials only contains one type of bonding?
Easy
- Agraphite
- Bbrass
- Cice
- Diodine crystals
3.Substance L has the following properties: melting point 660 °C; electrical conductivity: when solid — yes, when molten — yes. What is likely to be the identity of substance L?
Easy
- AGraphite
- BLi2O
- CNaCl
- DAl
4.What is the correct order of decreasing melting points for Group 1 metals?
Easy
- ANa > K > Rb > Cs
- BNa > K > Cs > Rb
- CCs > Rb > K > Na
- DK > Na > Rb > Cs
5.Which of the following metals would have the highest melting point?
Medium
- ANa
- BMg
- CAl
- DK
6.Which of the following species has the highest melting point? (Electron configurations are given.)
Medium
- A1s2 2s2 2p6 3s1
- B1s2 2s2 2p6 3s2
- C1s2 2s2 2p6 3s2 3p1
- D1s2 2s2 2p6 3s2 3p2
7.Which of the following metals will have the greatest ability to conduct electricity?
Medium
- ALi
- BMg
- CNa
- DAl
8.Sodium and magnesium are both Period 3 elements. Why is sodium more reactive than magnesium? (Select all that apply.)
Medium
- ASodium has a larger atomic radius
- BSodium has a smaller nuclear charge
- CSodium's outer electron is less strongly attracted to the nucleus
- DSodium has more delocalised electrons
- ESodium has a higher melting point

More questions

9.Metals are malleable because the layers of metal ions can slide over each other when a force is applied.
Easy
True or false?
10.Metals conduct electricity only in the solid state.
Easy
True or false?
11.Match each property of metals with its correct explanation.
Easy
- Malleable and ductile
- Electrical conductivity
- High melting and boiling points
- Layers of metal ions can slide over each other
- Delocalised electrons are free to move
- Strong electrostatic forces between cations and delocalised electrons
12.Which of the following statements about metallic bonding are correct? (select all that apply)
Medium
- AThe delocalised electrons are not bound to any specific atom.
- BThe metal ions are negatively charged.
- CThe electrostatic attraction is between positive metal centres and delocalised electrons.
- DMetals conduct electricity only when molten.
- EThe strength of the metallic bond increases as the charge on the metal ion increases.
13.Arrange the following Period 3 metals in order of increasing melting point.
Medium
- Na
- Mg
- Al
14.Which property of a metal is directly responsible for its ability to conduct heat?
Medium
- AThe closely packed lattice of metal ions.
- BThe mobility of delocalised electrons.
- CThe high density of the metal.
- DThe presence of a positive charge on the metal ions.
15.Which of the following statements best explains why magnesium has a higher melting point than sodium?
Medium
- AMagnesium has a smaller atomic radius and a 2+ charge, so it has stronger metallic bonding.
- BMagnesium has more delocalised electrons per atom, so it has stronger metallic bonding.
- CMagnesium has a larger atomic radius, so it has weaker metallic bonding.
- DMagnesium has a lower charge on its ions, so it has stronger metallic bonding.
16.Which factors increase the strength of a metallic bond? (select all that apply)
Medium
- AIncreasing the charge on the metal ion
- BIncreasing the number of delocalised electrons per metal atom
- CDecreasing the size of the metal ions
- DIncreasing the size of the metal ions
- EDecreasing the number of delocalised electrons
17.Which of the following explains why the melting point of potassium (337 K) is lower than that of sodium (371 K)?
Hard
- APotassium ions have a larger radius, so the attraction to the delocalised electrons is weaker.
- BPotassium ions have a smaller radius, so the attraction to the delocalised electrons is weaker.
- CPotassium has fewer delocalised electrons per atom than sodium.
- DPotassium has a higher charge on its ions than sodium.
18.A student adds a small piece of an unknown solid to water and observes that it reacts vigorously, producing a gas. The solid is a good conductor of electricity in both the solid and molten states. Which type of bonding is most likely present in the solid?
Medium
- AMetallic bonding
- BSimple molecular covalent bonding
- CIonic bonding
- DGiant covalent bonding
19.Which of the following statements about the thermal conductivity of metals are correct? (select all that apply)
Medium
- ADelocalised electrons carry kinetic energy rapidly through the metal.
- BCations vibrate more vigorously when heated and transfer kinetic energy to neighbouring cations.
- CThermal conductivity increases as the number of delocalised electrons per atom increases.
- DThermal conductivity is due to the movement of whole metal atoms through the lattice.
- EThermal conductivity only occurs when the metal is molten.
20.The electrical conductivity of a metal increases as you move from sodium to magnesium to aluminium.
Easy
True or false?
21.Match each metal property with its correct explanation.
Medium
- Malleability
- Electrical conductivity
- Thermal conductivity
- High melting point
- Layers of metal ions can slide over each other
- Delocalised electrons move towards the positive terminal
- Vibrating cations and free electrons transfer kinetic energy
- Strong electrostatic forces between cations and delocalised electrons
22.Arrange the following Period 3 metals in order of increasing electrical conductivity.
Medium
- Na
- Mg
- Al
23.Which of the following factors would increase the strength of a metallic bond? (select all that apply)
Hard
- AIncreasing the charge on the metal ion
- BDecreasing the radius of the metal ion
- CIncreasing the number of delocalised electrons per atom
- DIncreasing the size of the metal ion
- EDecreasing the number of delocalised electrons
24.The melting point of potassium is 337 K and that of rubidium is 312 K. Which statement best explains this difference?
Medium
- ARubidium has a larger ionic radius than potassium, so the electrostatic attraction between its cations and delocalised electrons is weaker.
- BRubidium has a higher charge than potassium, so the metallic bond is stronger.
- CPotassium has more delocalised electrons per atom than rubidium.
- DRubidium has a smaller ionic radius, leading to weaker metallic bonding.
25.A student heats a piece of sodium and a piece of magnesium separately until they melt. Which metal requires the higher temperature to melt, and what is the reason?
Medium
- AMagnesium, because its ions have a greater charge and a smaller radius, so the electrostatic attraction to the delocalised electrons is stronger
- BSodium, because it has more delocalised electrons per atom than magnesium
- CMagnesium, because it has a larger atomic radius, so its ions attract the electrons more strongly
- DSodium, because it is higher up Group 1 and so has stronger metallic bonding
26.A student sets up a circuit with a metal wire connected to a battery and a lamp. The lamp lights when the wire is connected. Which statement best explains the movement of charge in the wire?
Hard
- ADelocalised electrons move from the negative terminal to the positive terminal
- BDelocalised electrons move from the positive terminal to the negative terminal
- CPositive metal ions move from the negative terminal to the positive terminal
- DPositive metal ions move from the positive terminal to the negative terminal
27.A student wants to compare the thermal conductivity of copper and iron. Which experimental method would be most suitable?
Medium
- AAttach a drawing pin to each rod using wax and heat one end of each rod, timing how long it takes for the pin to fall
- BMeasure the electrical resistance of each rod using a multimeter
- CPlace each rod in water and measure the volume of water displaced
- DHeat each rod to melting point and record the temperature
28.A student investigates the electrical conductivity of four metals: sodium, magnesium, aluminium and potassium. All are tested as solid rods of the same length and cross-sectional area. Which metal is expected to give the highest current?
Medium
- AAluminium
- BMagnesium
- CSodium
- DPotassium
29.A student adds a small piece of an unknown metal to cold water. The metal reacts vigorously, fizzing and moving rapidly across the surface. The resulting solution is tested with universal indicator and turns purple. Which metal is most likely to be the unknown?
Hard
- APotassium
- BMagnesium
- CAluminium
- DCopper
30.A student is comparing the melting points of sodium, magnesium and aluminium. Which of the following factors explain why aluminium has the highest melting point of the three? (select all that apply)
Hard
- AAluminium ions have a 3+ charge, giving a greater charge difference with the delocalised electrons
- BAluminium has more delocalised electrons per atom than sodium or magnesium
- CAluminium ions have a smaller radius than sodium or magnesium ions
- DAluminium has a larger atomic radius, which increases the attraction to electrons
- EAluminium has weaker metallic bonding because it has more electrons
31.Metals can conduct electricity in both the solid and liquid states.
Medium
True or false?
32.When a metal is heated, the delocalised electrons are primarily responsible for conducting heat because they are not bound to any specific atom and can move freely.
Medium
True or false?
33.What name is given to the electrons that are free to move throughout a metal lattice?
Easy
- ADelocalised electrons
- BValence electrons
- CFree radical electrons
- DIonic electrons
34.Which statement best describes the structure of a metal?
Easy
- APositive metal ions in a sea of delocalised electrons
- BNegative metal ions in a sea of delocalised protons
- CNeutral metal atoms held by covalent bonds
- DPositive metal ions held by ionic bonds to negative non-metal ions
35.Metallic bonding is the electrostatic attraction between positive metal ions and delocalised electrons.
Easy
True or false?
36.Which of the following is NOT a typical property of a metal?
Easy
- ABrittle and easily shattered
- BMalleable and ductile
- CGood conductor of electricity
- DHigh melting point
37.Which of the following properties are typical of metals? (select all that apply)
Medium
- AGood electrical conductivity
- BGood thermal conductivity
- CMalleability
- DBrittleness
- ELow melting point
38.Why are metals good conductors of heat?
Medium
- ADelocalised electrons and vibrating cations transfer kinetic energy rapidly through the lattice
- BThe metal ions are free to move throughout the lattice
- CThe metal lattice contains trapped air pockets that circulate heat
- DHeat causes the metal ions to break apart and reform, releasing energy
39.Which factor would increase the strength of a metallic bond?
Medium
- AIncreasing the charge on the metal ion
- BIncreasing the radius of the metal ion
- CDecreasing the number of delocalised electrons
- DDecreasing the number of positive charges on the metal centres
40.Which of the following correctly describes the trend in melting points of the Group 1 metals as you go down the group?
Medium
- AMelting point decreases
- BMelting point increases
- CMelting point stays the same
- DMelting point first increases then decreases
41.What name is given to the free-moving electrons in a metal lattice?
Easy
42.Complete the sentence about metallic bonding.
Easy
In a metal lattice, the positive metal ions are attracted to the ____ electrons.
43.The melting point of sodium is 371 K. What is this temperature in °C? (Give your answer to the nearest whole number.)
Medium
44.The melting point of aluminium is 933 K. Convert this temperature to degrees Celsius. Give your answer to the nearest whole number.
Medium
45.Complete the sentence about the trend in melting points of Group 1 metals.
Easy
As you go down Group 1, the melting point ____ because the ionic radius ____.
46.Give the name of the alloy formed when copper is combined with zinc.
Medium
47.The melting point of magnesium is 922 K. Convert this temperature to degrees Celsius. Give your answer to the nearest whole number.
Medium
48.Complete the sentence about the structure of metals.
Medium
In a metal lattice, the positive ions are surrounded by a sea of ____ electrons, which are free to move and are described as ____.
49.Name the property of metals that allows them to be drawn into wires.
Medium
50.The melting point of magnesium is 922 K. Convert this temperature to degrees Celsius, giving your answer to the nearest whole number.
Easy
51.The melting point of potassium is 337 K. Convert this temperature to degrees Celsius, giving your answer to the nearest whole number.
Easy
52.A sample of aluminium has a melting point of 933 K. Express this temperature in °C, to the nearest whole number.
Medium
53.Describe the bonding in solid sodium.
Medium
54.Potassium has a lower melting point than sodium. Explain why.
Medium
55.Magnesium is in the same period as sodium, but has a much higher melting point. Explain why.
Medium
56.Predict whether magnesium is harder or softer than sodium and explain why.
Medium
57.Copper is a common metal used in wiring. Explain the electrical conductivity of copper.
Medium
58.The melting point of sodium is 371 K. What is this temperature in °C? (Give your answer to the nearest whole number.)
Medium
- A108 °C
- B98 °C
- C118 °C
- D88 °C
59.The melting point of aluminium is 933 K. Convert this temperature to degrees Celsius. Give your answer to the nearest whole number.
Medium
- A792 °C
- B726 °C
- C660 °C
- D594 °C
60.The melting point of magnesium is 922 K. Convert this temperature to degrees Celsius. Give your answer to the nearest whole number.
Medium
- A584 °C
- B714 °C
- C649 °C
- D779 °C
61.The melting point of magnesium is 922 K. Convert this temperature to degrees Celsius, giving your answer to the nearest whole number.
Easy
- A714 °C
- B779 °C
- C649 °C
- D584 °C
62.The melting point of potassium is 337 K. Convert this temperature to degrees Celsius, giving your answer to the nearest whole number.
Easy
- A58 °C
- B70 °C
- C76 °C
- D64 °C
63.A sample of aluminium has a melting point of 933 K. Express this temperature in °C, to the nearest whole number.
Medium
- A792 °C
- B660 °C
- C594 °C
- D726 °C

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