Which of the nine substances are made of three elements?

What mass of carbon dioxide is produced from the complete combustion of 4.50×10−3 g of methane?

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.

Frictional forces acting on an object are often converted into energy, which causes the temperature of the object to rise slightly.