If something is broken into pieces will it weight more or less

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.

If you have 5.25 grams of methane (ch4), how many grams of co2 will you produce ?

Find the midpoint of a segment with endpoints of 4-3i and -2+7i