An element has a mass of 39.2 and an atomic number of 19. How many protons does this element have? How many neutrons? How many electrons?

19 protons, 19 electrons, and 3 neutrons

Explanation:

the atomic number is 19 so the protons are the same, 19, and the electrons are the same as the proton, because protons are positive and electrons are negative so they have to balance out and the neutrons ➗ mass number by the atomic number.

the law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. because atoms are only rearranged in a chemical reaction, there must be the same number of sodium atoms and chlorine atoms in both the reactants and products