| Answer | Crossword Clue |
|---|---|
| ASTATINE | Rarest naturally occurring element in the earth's crust |
| OXYGEN | Most abundant element in the earth's crust |
| SODIUM | Sixth most abundant element in the Earth's crust |
| SILICIC | Pertaining to the second most common element in the Earth's crust |
| silicon | nonmetallic element that constitutes more than one fourth of the earth's crust in its combined forms |
| superheavy | Relating to or denoting an element with an atomic mass or atomic number greater than those of the naturally occurring elements, esp. one belonging to a group above atomic number 110 having proton/neutron ratios that in theory confer relatively long half-lives |
