The elements on the periodic table are arranged in order of increasing
(1) atomic mass
(2) atomic number
(3) first ionization energy
(4) selected oxidation state

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom