Can anyone help me with #3? Please and Thank you!

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.

When water dissociates, each water molecule splits into a hydroxide ion and a) h 3 o + b) a hydrogen atom c) a hydrogen ion d) h 2 o e) oh —

If two objects at different te,peraure are in contact with each other what happens to their temperature