Protons are important to human body why

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion

Which factor is likely to impact the possible number of compounds ?

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.