Gold's Unreactivity Makes It Useful

What students typically write

“Gold is at the bottom of the reactivity series so it can’t be used for anything useful.” Or: “Unreactive metals are not useful because they don’t react.”

Students equate reactivity with usefulness. In their mental model, a useful metal is one that does things (reacts). An unreactive metal therefore seems like a passive, useless substance.

Why it is wrong

Usefulness and reactivity are not the same thing. Many applications require a metal that does NOT react. Gold’s position at the bottom of the reactivity series is exactly what makes it valuable.

Jewellery: Gold does not tarnish or corrode, so it stays shiny and attractive indefinitely. Iron jewellery would rust. Copper jewellery turns green. Gold remains unchanged for thousands of years (Egyptian gold artefacts still gleam).

Electronics: Gold-plated connectors in computers, phones, and audio equipment provide reliable electrical contact because gold does not form an oxide layer. Other metals develop oxide coatings that increase resistance and degrade connections.

Dentistry: Gold fillings and crowns do not react with saliva, food acids, or mouth bacteria. The inertness means they last for decades without degrading.

The general principle: a metal’s position in the reactivity series determines its uses. Reactive metals like sodium are useful as reducing agents. Unreactive metals like gold and platinum are useful where durability and resistance to corrosion matter.

What the mark scheme actually wants

A typical question: “Explain why gold is used for electrical connectors rather than iron.” [2]

Marking points:

1. Gold does not corrode / is unreactive / does not form an oxide layer (1 mark)
2. Iron would corrode / rust, which would increase resistance / reduce conductivity (1 mark)

The marks reward understanding that unreactivity is the useful property.

Worked example: wrong vs right

Question: Gold is found uncombined in the Earth’s crust, while iron is found as iron oxide. Explain why, and state one advantage of gold’s unreactivity. [3]

Wrong answer: “Gold is found uncombined because it is useless and doesn’t react. Iron oxide is more useful because it can be turned into iron.” This scores 0-1/3. The explanation for gold being found uncombined is partially there but framed as a disadvantage.

Right answer: “Gold is very unreactive / below carbon in the reactivity series, so it does not react with oxygen or other elements in the Earth’s crust and is found as the native metal (1). Iron is more reactive and combines with oxygen over time to form iron oxide (1). Gold’s unreactivity is an advantage because it does not corrode, making it suitable for jewellery and electrical connectors (1).” This scores 3/3.

How to avoid this mistake

When the reactivity series comes up, remember that both ends are useful, for opposite reasons. Highly reactive metals are useful where you need a vigorous reaction (sodium in street lamps, magnesium in flares). Unreactive metals are useful where you need permanence and resistance to chemical change.

For the full reactivity series and metal uses, see reactivity series and properties of metals.