A student is given a small sample of a pure solid substance. She is asked to identify the substance based on a particular property. Which property, if determined accurately, would best help her identify the substance?

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

Over the last 90 years, scientists have added to the body of evidence supporting the big bang theory. what is the latest piece of evidence discovered in 2014?

Compare and contrast the bohr model and the electron cloud models of the atom.