The individual molecule will still exhibit all the qualities that would be associated with a large sample of the compound. Percent of Abundance refers to the quantity of a specific isotope that occurs in a natural sample of an element. It has been established that the distribution of the elements on Earth is such that a natural sample of an element will contain the same percent of abundance of a given isotope, no matter where the sample was obtained. A physical change is a change in the appearance of a substance. The original properties of the substance remain the same, but the substance looks different.
Phase changes are some of the more common examples of physical changes.
For instance, if ice melts into liquid water, then the product looks different from ice. It is still water, however. The Planetary Model of the atom was developed by Rutherford . It was one of the first significant attempts to describe the atom as chemists know it today. The model describes the atom as being a small volume nucleus that concentrates the vast majority of the atom's mass.