Drop a lump of potassium into water and it fizzes, spits and bursts into lilac flame. Drop a gold ring into water and… nothing. Same family — metals — but opposite ends of the reactivity series.
The reactivity series
The reactivity series lists metals from most reactive at the top to least reactive at the bottom. A rough order to know: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold. The higher a metal sits, the more eagerly it reacts.
Metals with acids
Most metals react with acids following one reliable pattern:
The gas given off is always hydrogen, which you can hear as fizzing. A more reactive metal fizzes faster and more vigorously; a less reactive one barely reacts at all. So the speed of the fizz is a clue to where the metal sits in the series.
Displacement reactions
Here is the key rule: a more reactive metal will displace (push out) a less reactive metal from its compound. Think of it like a game of musical chairs where the stronger player takes the seat. Add magnesium to blue copper sulfate solution and the magnesium — being higher in the series — kicks the copper out, so copper metal appears and the blue colour fades.
| Metal | Position | Found in nature as |
|---|---|---|
| Potassium, sodium | Most reactive | Locked in compounds |
| Iron, zinc | Middle | Mostly in ores |
| Gold, silver | Least reactive | Often the pure metal |
This is why gold is dug up as shiny nuggets — it is too unreactive to combine with anything — while reactive metals are always trapped in compounds and must be extracted.
Worked reasoning
Ask: "which metal is more reactive?" Magnesium is higher in the series than copper.
So magnesium displaces the copper: it takes copper's place in the compound, and copper metal is released. The blue solution fades as the copper drops out.
Memory hook: reactive metals are needy — they cling to compounds and shove weaker metals aside; gold is a loner found pure.