Which statement is true about a polyatomic ion?

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 step in naming unsaturated hydrocarbons is used for alkenes but not alkynes

Which of the following would be an accurate picture of the earth during the summer time of the northern hemisphere?