Element 37 in our International Year of the Periodic Table series is rubidium. Used in GPS satellites and in some types of perovskite solar cells, one of its isotopes can also be used to locate and image brain tumours.

Rubidium is at the more reactive end of group 1 of the periodic table. This means that, though you’re likely to have seen its predecessors, lithium, sodium and potassium, in school chemistry lessons, rubidium won’t have made an appearance. The latter metals fizz, pop, and (in potassium’s case) burst into flames when added to water; rubidium’s reaction with water is a lot more violent, and a lot less safe for school laboratories!

Its reactivity means that rubidium in its elemental form is limited in its uses. However, one use is in satellites that enable us to use GPS on our phones. Rubidium atomic clocks use transitions of electrons in rubidium-87 atoms to help keep accurate time. Caesium atomic clocks are even more accurate. Both types are used in the satellites that make GPS possible.

GPS satellites are constantly transmitting the time (from the atomic clocks) and their location. This can be picked up by receivers in our electronic devices. By receiving the information from multiple satellites, and using the time delay between the signal being sent and received, your device is able to work out your position accurately.

Rubidium ions are used in perovskite solar cells to improve their material properties and increase their efficiency. While perovskites have yet to better other commercial solar cells, their potential to reach higher efficiencies and their cheaper production costs means that a lot of research is focused on developing them.

Finally, a radioactive isotope of rubidium, rubidium-82, can be used to locate and image brain tumours. This is possible because it’s selectively concentrated in tumour tissue.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.