| 1 | Even Francium's most stable isotope, Francium-223 only has a half-life of 22 minutes. | |
| 2 | Any of the monovalent metals of group I of the periodic table (lithium or sodium or potassium or rubidium or cesium or francium). | |
| 3 | Because Francium is mainly only found synthetically in laboratory research, it has no known use outside of the laboratory. | |
| 4 | So little is known about it, because there is only about 1 ATOM OF FRANCIUM IN A CUBIC FOOT OF URANIUM ORE! | |
| 5 | 金属镓在室温里是固体状态但是把它放在你的手上它就会融化,金属铯,元素钫这些比较稀有的元素在室温或者接近室温的情况下是液体状态的。 Gallium is solid at room temperature but will melt if held in your hand, caesium (Cs), and francium (Fr) ?the second rarest naturally occurring element, can also be liquid at or near room temperature. |