| Krypton is the fourth member of Group 18 of the periodic table, a group of elements known as the noble gases or inert gases. |
| It combines with all elements except the noble gases of Group 18 of the periodic table. |
| The noble gases helium, neon, argon, krypton, and xenon display fairly simple chemistry in material of solar composition. |
| Four important chemical family names of elements still widely used are the alkali metals, the alkaline earths, the halogens, and the noble gases. |
| Fluorine is so reactive that it forms compounds with the noble gases, which were thought to be chemically inert. |
| Two copies of the column with the noble gases, such as helium and neon, bracket the table like bookends. |
