An atom of ruthenium (Ru) contains 44 protons and 44 electrons. The number of protons in the nucleus of an atom determines its atomic number and identifies the element. Ruthenium has an atomic number of 44, which means that each atom of ruthenium contains 44 positively charged protons. To maintain electrical neutrality, an atom must have an equal number of positively charged protons and negatively charged electrons. Therefore, an atom of ruthenium also contains 44 negatively charged electrons.