Is this molecule a polar or non polar?

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.

Asample of aluminum foil contains 8.60 × 1023 atoms. what is the mass of the foil?

For each of the compounds below, show that the charges on the ions add up to zero. a. kbr b. cao c. li(2)o d. cacl(2) e. alcl(3)