What changes to the Earth's surface might benefit humans

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.

What is the percent by mass of oxygen in fe2o3

What type of chemical reaction occurs between silver nitrate (agno3) and copper (cu)? the equation i was given is 2agno3 + cu —> 2ag+ cu(no3)2.