What is the difference between mass number and atomic number?

What is the indicator of the number of ions in solution? the amount of conductivity the amount of precipitate the amount of solute added

Draw the aromatic compound toluene (methylbenzene). show all hydrogen atoms, including those on the ring.

What do electromagnetic waves carry? how are they produced through which media can they move? where do they transfer energy? what do they not transfer? what do mechanical waves carry? how are they produced? through which media can they move? where do they transfer energy? what do they not transfer?