1.1.2Building Blocks for Understanding
Metals and Non-Metals — AQA GCSE Combined Science Synergy 8465 - Physical Sciences Revision Notes & Topical Questions
5 min read 7 parts Lesson 3 of 14
Section 1 of 7Position on the periodic table
Metals
- Metals Most elements are metals, found to the left and centre of the table.
- A staircase line separates them from non-metals on the right.
Non-metals
- Non-metals Non-metals sit in the top right of the table, including hydrogen, carbon, nitrogen, oxygen, the halogens and the noble gases.
Electron arrangement
- Electron arrangement Elements in the same group have the same number of outer-shell electrons, which is why they react in similar ways.
- A group number equals the number of outer electrons (except Group 0).
Section 2 of 7Comparing properties
| Property | Metals | Non-metals |
|---|---|---|
| Appearance | Shiny when polished | Dull |
| Strength | Strong, malleable, ductile | Brittle when solid |
| Melting and boiling points | Usually high | Usually low |
| Electrical conduction | Good conductors | Poor conductors (graphite is an exception) |
| Thermal conduction | Good conductors | Poor conductors |
| Density | Usually high | Usually low |
| Oxides in water | Basic | Acidic |
Section 3 of 7Why metals conduct
1Outer electrons delocalise
- Outer electrons delocalise Metal atoms lose outer-shell electrons into a shared sea.
2Positive ions in a lattice
- Positive ions in a lattice Layers of ions are held by attraction to the electrons, which is the metallic bond.
3Charge flows
- Charge flows Delocalised electrons move through the structure and carry charge and thermal energy.
4Layers slide
- Layers slide The layers of ions can slide over each other without breaking the bond, so metals bend instead of shattering.
Section 4 of 7Forming ions
Ion formation
Metals lose electrons
- Metals lose electrons Metal atoms give up outer electrons to form positive ions, such as Na+ and Mg2+.
Non-metals gain electrons
- Non-metals gain electrons Non-metal atoms gain electrons to form negative ions, such as Cl- and O2-.
Aim of the change
- Aim of the change Atoms achieve a full outer shell like a noble gas.
Section 5 of 7Worked example: working out the ion
1
Find the group number: magnesium is in Group 2, so it has two outer electrons.
2
Metals lose their outer electrons, so magnesium loses two electrons.
3
Losing two negative charges leaves two extra positive charges, giving Mg2+.
4
For oxygen in Group 6, six outer electrons means two more are needed, giving O2-.
5
The compound magnesium oxide, MgO, is neutral because 2+ and 2- cancel.
Section 6 of 7Key terms
| Term | Meaning |
|---|---|
| Metal | An element that forms positive ions and conducts electricity. |
| Non-metal | An element that forms negative ions or shares electrons and generally does not conduct. |
| Malleable | Able to be hammered or bent into shape without breaking. |
| Ductile | Able to be drawn into wires. |
| Delocalised electrons | Outer electrons that are free to move through a structure. |
| Ion | An atom or group of atoms with an overall electrical charge. |
Section 7 of 7Exam technique
1
Writing that all non-metals are gases; carbon, sulfur and phosphorus are solids and bromine is a liquid.
2
Forgetting that metals form positive ions by losing electrons, not by gaining them.
3
Saying metals conduct because their atoms move; it is the delocalised electrons that carry charge.
4
Giving graphite as a metal when it is a non-metal that happens to conduct.
5
Assuming mercury is solid. It is a metal that is liquid at room temperature.
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