| Lighter-than-air party balloons are filled with ____. |
carbon (C) |
| The most malleable and ductile metal element is ____. |
gold (Au) |
| A dense, radioactive, noble gas is ____. |
helium (He) |
| All ____ atoms have six protons. |
hydrogen (H) |
| About 78% of the Earth's atmosphere is ____. |
lead (Pb) |
| The lightest and most abundant element in the Universe is ____. |
nitrogen (N) |
| The metal with the highest electrical conductivity is ____. |
radon (Rn) |
| A very heavy, stable metal used to shield radiation is ____. |
silver (Ag) |
