When cut, the atoms on the surface of the gold choose a hexagon arrangement. This configuration reduces the ability to bind to oxygen billions of times, making the metal immune to oxidation.
What makes gold so special is not so much its color, but the fact that that color never changes. Gold is the king of metals due to the fact that it is not affected by any other substance except an acid called aqua regia. In particular, its surface does not attract oxygen atoms present in the air to itself, as iron and copper do. But it’s not clear why.
Hexagonal
To understand this, a team from Tulane University in New Orleans (USA) simulated the behavior of atoms on gold surfaces on the computer. A metal oxidizes (the technical term for the process that leads to rust) because its surface exerts an attraction on oxygen molecules in the surrounding air, separating the two atoms that make up each molecule.
The atoms thus freed can bond with those of the metal and form new compounds. The researchers discovered, and reported in Physical Review Letters, that – when a piece of gold is cut or worked – the atoms on its surface can be found in multiple configurations, forming rectangles, squares or hexagons.
Under normal conditions, they tend to reorganize rapidly by “choosing” the hexagonal structure, which is the one that requires less energy to be stable. However, it is also the least capable of attracting oxygen: as soon as the gold atoms arrange themselves into hexagons, their ability to combine with oxygen decreases billions of times. If atoms maintained a square or rectangular configuration, even the king of metals would rust. And if a way could be found to force them into that configuration even temporarily, catalysts for CO2 capture or the production of “green” plastics could be obtained.
