An atom of an element has 54 protons. some of the element's atoms have 77 neutrons, while other atoms have 79 neutrons. what are the atomic numbers and mass numbers of the two types of atoms of this element

Which of these properties, used alone, would be least useful in identifying most minerals? a. color b. luster c. streak d. density

What is the molarity of the solution produced when 145 g of nacl is dissolved in sufficient water to prepare 2.75 l of solution?

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.