Four new elements were discovered and added to the periodic table. That’s a 13 ______ deal! The atoms of the elements are so 14 ______ that half a million of them could line up across a single human hair. Atoms are made up of protons, neutrons and electrons. Different atoms have different amounts of them which 15 ______ tell us what kind of element it is. An element can’t be broken down any further. And 16 ______ element has its own personality or characteristic. A Russian scientist named Mendeleev figured all of this out and 17 ______ the elements into a chart  — The Periodic Table of Elements. He even knew, in 1869, that there would be more elements discovered. And we’re still adding them nearly 150 years 18 ______! This is the first time in 5 years that any have been added.