Which property makes it possible to separate the oxygen and the nitrogen from a sample of iquefied air?
(1) boiling point (3) hardness
(2) conductivity (4) electronegativity

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.

Which of the following happens during cell division? (a) energy is created (b) waste is eliminated (c) carbon dioxide is released (d) damaged cells are replaced

What is the mass of 4 molecules of co2