AQA Chemistry 5.1.2.3
Metals and non-metals
One difference decides it: metals form positive ions, non-metals do not. Every other difference follows from the outer electrons.
Triple Science · Higher tier
Start here
Kitchen foil and a pencil lead.
Take a strip of kitchen foil and the thin grey lead from a mechanical pencil. The lead is graphite, a form of carbon. Try to bend each one in half.
If you had to guess, which one bends without snapping?
The definition · outer electrons
Metals react to form positive ions. Non-metals do not.
A metal atom has 1, 2 or 3 outer electrons. When it reacts it loses them and forms a positive ion. A non-metal atom has 4 to 7 outer electrons, so it gains or shares electrons instead, or it has a full outer shell (Group 0). The number of outer electrons is the group number, so it also sets where the element sits. Pick an element.
Sodium · Group 1, period 3 · 2, 8, 1
Metal
1 outer electron. When it reacts it loses it and forms a + ion.
Most elements are metals. Metals are found to the left and towards the bottom of the periodic table; non-metals towards the right and top. Hydrogen sits on its own at the top.
Test bench · two unknown elements
Run three tests, then decide.
Pick a sample and run each test. When you have all three results, say whether it is a metal or a non-metal.
Sample A: a dull yellow powder.
Does it conduct?
Hammer it
Oxide in water + indicator
Two exceptions to know
Most non-metals are small molecules with weak forces between the molecules, so they have low melting and boiling points. Carbon (diamond and graphite) and silicon are giant structures with very high melting points. Graphite and graphene, forms of carbon, conduct electricity because one electron from each carbon atom is delocalised. Why is taught in the bonding lessons.
Think again · lose or gain
“Metals gain electrons when they react.”
Your call
ChooseMagnesium has 2 outer electrons. What happens to them when magnesium reacts?
Sort
Metal or non-metal?
Place each property.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Identify
- Use the evidence given: conducts, bends, oxide acidic or basic.
- Explain
- Start from the outer electrons: how many, then lost, gained or shared.
- Compare
- Say the property for both elements, side by side.
Key fact
Elements that react to form positive ions are metals. Elements that do not form positive ions are non-metals.
Key note · AQA 5.1.2.3
Metals and non-metals
- Elements that react to form positive ions are metals. Elements that do not form positive ions are non-metals.
- Most elements are metals: to the left and towards the bottom of the periodic table. Non-metals are towards the right and top.
- Metals have 1 to 3 outer electrons, lost when they react. Non-metals have 4 to 7 (gained or shared) or a full outer shell.
- Metals: conduct, high melting points, malleable and ductile, basic oxides.
- Most non-metals: poor conductors, low melting points (small molecules), brittle, acidic oxides.
- Exceptions: graphite and graphene conduct; carbon and silicon have very high melting points.
Photograph this card. Tomorrow, cover it and say each line first.
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Ask MrBadmus
Not sure why outer electrons decide it?
The table shows elements 1 to 20 only. Atom diagrams are not to scale.