Does gold react with oxygen?

Reactivity at Standard Conditions

At standard temperatures and pressures, metallic gold does not react with oxygen gas. Gold is considered a noble metal because it resists oxidation and corrosion. The stable electronic configuration of gold makes it very chemically inert.

When gold is exposed to air or oxygen, no discernible oxidation or tarnishing occurs. This resistance to oxygen is why gold maintains its shine and luster over time.

Reactivity at High Temperatures

However, gold can react with oxygen if it is extremely finely divided and heated to over 250°C. Under these conditions, the oxygen molecules have enough energy to oxidize the surface atoms of the gold:

2Au(s) + 3/2O2(g) → Au2O3(s)

This produces a purple or brown gold(III) oxide powder. Heating the oxide above decomposition temperature (about 350°C) will dissociate it back to elemental gold and oxygen gas.

Real-World Significance

In most real-world applications, gold does not reach high enough temperatures for significant oxidation by oxygen to occur. So for all practical purposes, gold is unreactive with oxygen under ambient conditions.

The lack of oxidation is why gold can maintain its shine and withhold corrosion for thousands of years. Oxygen in the atmosphere does not tarnish metallic gold, enabling it to retain its coveted luster.

So in summary, while gold can technically react with oxygen at high temperatures, at normal conditions it is essentially inert and highly resistant to oxidation. This allows gold to maintain its prized chemical stability in air over very long time periods.