Organization of Periodic Table

The arrangement of the elements in the periodic table may seem odd at first. But there is actually a reason for its arrangement. Each row (known as a period) of the periodic table starts with elements that have a lower atomic weight. For example, Lithium (Li) weighs less than Beryllium (Be) which weighs less than boron (B), and so on across the row. The next row down (which starts with sodium (Na)) contains elements that have increasingly larger atomic masses; this pattern continues down the periodic table of elements.

The columns (known as groups) are set up to have similar elements close together. Click the "groups" menu on the interactive periodic table and you will see a list of groups. Select "noble gases." Do you see the far right column highlighted in purple? That's because all the noble gases react with other elements in the same way. You do not need to know right now the properties of each group, only that the periodic table is arranged to put similar elements together.