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3.5Chapter 3: Metals and Non-Metals

Explaining metal and non-metal properties — Alhussan Chemistry - Stage 7 Revision Notes & Topical Questions

5 min read 9 parts Lesson 5 of 7 3 quizzes

📚 Alhussan Chemistry - Stage 7 Hub / Topical Revision
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Lesson summary

3.5 Explaining metal and non-metal properties — Alhussan International Academy — Chemistry (Stages 7–9) notes: Explain the physical properties of metals and non-metals in terms of how their particles are arranged and held together.PropertyMetalsNon-metalsAppearanceShinyDull when …

  • Delocalised electrons
  • Metallic bonding
  • High melting points
  • Conductivity
  • Malleable and ductile
  • Low melting points

Part 1 of 7Typical properties

PropertyMetalsNon-metals
AppearanceShinyDull when solid
State at 20 °CMostly solid (mercury is liquid)Many are gases
ConductivityGoodPoor (graphite is an exception)
ShapingMalleable and ductileBrittle
Melting and boiling pointsHighMostly low
StrengthStrongWeak when solid
SoundSonorousNot sonorous
  • Method
    • consider how the particles are arranged and how strongly they are held together.

Part 2 of 7Metallic bonding

Metallic bonding
Structure
  • Structure in a metal the atoms are packed closely in regular layers.
Delocalised electrons
  • Delocalised electrons the outer electrons are not held to one atom but move freely throughout the structure.
Metallic bonding
Metallic bonding the attraction between positive metal ions and the sea of delocalised electrons.

Part 3 of 7Explaining metal properties

High melting points
  • High melting points the atoms or ions are held together strongly, so much energy is needed to overcome the attraction.
  • Most metals are therefore solid at 20 °C.
Strength
  • Strength the particles are held together strongly, especially when mixed with other elements in alloys.
Conductivity
  • Conductivity the free electrons carry electric charge and pass on energy rapidly when heated.
Malleable and ductile
  • Malleable and ductile layers of atoms can slide over each other without breaking the bonding,
    • because the electrons keep holding the structure together.

Part 4 of 7Explaining non-metal properties

Low melting points
  • Low melting points most non-metals exist as single atoms or molecules that are attracted to each other only weakly.
  • Helium, neon, argon and krypton exist as single atoms.
  • An oxygen molecule has two atoms held tightly together, but the molecules are attracted to one another only weakly.
Small molecules
  • Small molecules most non-metals such as O2 and S8 have strong covalent bonds inside the molecule but weak forces between molecules.
  • Little energy is needed to separate the molecules, so many are gases.
  • Low melting points are explained by weak forces between molecules, not weak bonds inside molecules.
No conduction
  • No conduction there are no free electrons, so non-metals do not conduct electricity.
Brittleness
  • Brittleness iodine exists as two-atom molecules arranged in a pattern in the crystal.
  • Molecules are attracted weakly, so a dropped crystal breaks between one row of molecules and another.
  • The pieces have straight edges.

Part 5 of 7Giant non-metal structures

Giant non-metal structures
Diamond
  • Diamond every carbon atom is bonded to four others in a rigid network, so it is extremely hard with a very high melting point but does not conduct.
Graphite
  • Graphite carbon atoms form layers in which each atom has a spare electron that can move along the layer.
  • It conducts electricity.
  • The layers slide easily, so it is soft and used in pencils.

Part 6 of 7Choosing materials

Metals suit cables, pans and structures.
  • Copper is used for wires because free electrons conduct electricity and it is ductile.
Non-metals
  • Non-metals plastics, made largely from carbon compounds, suit insulation.
Exceptions
  • Exceptions silicon is a shiny solid and a semiconductor, and mercury is a liquid metal, which shows that classification is a model.

Part 7 of 7Link to the periodic table

Boundary
  • Boundary a stepped line separates metals from non-metals.
Metalloids
  • Metalloids elements next to the line, such as silicon and germanium, look metallic but behave in between.
  • Silicon is a semiconductor, used in microchips and solar cells.
Oxides
  • Oxides metal oxides are usually basic and non-metal oxides acidic.

Key terms

TermMeaning
Delocalised electronsOuter electrons that move freely through a metal.
Metallic bondingAttraction between metal ions and delocalised electrons.
Covalent bondA bond in which atoms share electrons.
BrittleBreaking easily when hit.
MetalloidAn element with properties between metals and non-metals.
SemiconductorA material that conducts electricity only partly.

Avoid these mistakes

1
Saying all non-metals are gases.
2
Saying graphite is a metal because it conducts.
3
Thinking electrons in metals flow only when a cell is connected — they are always free to move but flow in one direction only with a voltage.
4
Explaining low melting points by weak bonds inside molecules rather than weak forces between molecules.

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