Cracking the periodic table code why aren't the elements listed in alphabetical order answer key

They could be arranged in alphabetical order but that wouldn't tell you much about their chemistry. In the periodic table, the elements are arranged according to their atomic number. Notice how the atomic number increases as you move across the table. Normally, the higher the atomic number, the heavier the element. So lead (Pb), atomic number 82 is heavier than tin (Sn) atomic number 50.