How is the sea of electrons model is used to explain the physical properties of metals? electrons give off a charge, the greater or lesser the metal will depend on how packed the universe is in the metal, atoms and such.
Mutations can also be caused by exposure to specific chemicals or radiation. These agents cause the DNA to break down. This is not necessarily unnatural  even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair.
Chemicals and radiation can damage genes. However, most mutations occur when the cell makes errors as it copies its genes. Genes are made out of DNA, a chemical code with four different 'letters'. Each time one of your cells divides, it must copy around 6000 million letters of DNA code. Occasionally, mistakes are made, causing mutations.