Explanation:
The atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. This means that the number.
That means 12.01 grams of carbon contains 6.0225*1023 atoms of carbon. If you divide the atomic weight by Avogadro's number, you get the mass of one atom. In the case of carbon, that ends up being 0.000000000000000000000019942 grams.
The number of protons is the atomic number, and the number of protons plus neutrons is the atomic mass. For hydrogen, the atomic mass is 1 because there is one proton and no neutrons. For helium, it is 4: two protons and two neutrons.
The vertical columns on the periodic table are called groups or families because of their similar chemical behavior. All the members of a family of elements have the same number of valence electrons and similar chemical properties. The horizontal rows on the periodic table are called periods.
