Is a pure element a heterogenous or homogeneous mixture and why

The identities of substances are the same before and after which type of change

What is the molecular weight of copper

Which statement best summarizes the importance of ernest rutherford’s gold foil experiment? it proved that all of john dalton’s postulates were true. it verified j. j. thomson’s work on the atomic structure. it showed that an electron circles a nucleus in a fixed-energy orbit. it showed that a nucleus occupies a small part of the whole atom.