Gold is the most malleable element, according to Mike Bullivant, a chemist at The Open University in Milton Keynes, England. It’s so malleable, it can be hammered to be thinner than a wavelength of visible light, noted a 1977 study from the University of Leeds in England. But why is gold so malleable?
First, it’s important to distinguish malleability from softness. Malleability is a measure of how much a material can be hammered into a new shape without breaking. Whereas other metals fragment when beaten past a certain point, a single ounce (28 grams) of gold can be hammered into a sheet measuring roughly 16.4 feet (5 meters) on a side, and films of gold known as gold leaf can be as thin as five-millionths of an inch (0.000127 millimeters), or about 400 times thinner than a human hair, according to Jefferson Lab in Newport News, Virginia.
In contrast, there are multiple definitions of hardness and softness, depending on how one tests a material’s strength. Based on the Mohs scale, which measures how well a material resists scratching, the softest metal is cesium, which is soft enough to be cut with a butter knife, according to Guinness World Records. Arguably, the softest metal may be mercury, which “is a liquid at room temperature and is more easily deformed than gold,” Mark Jones, a chemistry consultant and fellow of the American Chemical Society, told Live Science. “It is, by my estimation, softer than gold.”