NOVA Hunting the Elements Practice Test

Heavy is about density, which is how much mass sits in a given volume. Gold has a very high density because its atoms are heavy (lots of protons and neutrons) and they pack together tightly in a solid crystal. That combination means a small chunk of gold weighs more than the same-sized chunk of many other materials—about 19.3 g per cubic centimeter at room temperature. The other properties describe other traits (how easily it melts, how it reacts, or how heavy the atoms themselves are in a different sense), but they don’t determine why gold feels so heavy.