Q: Does every element in the Periodic Table have a practical use?

THE Periodic Table is an elegant arrangement of chemical elements ordered by their atomic number and properties. Created by Russian chemist Dmitry I. Mendeleyev in the mid-19th century, it has been invaluable in the development of chemistry.

Most of the first 92 elements have some practical use while none of the chemical elements with atomic numbers higher than 98 – from einsteinium (99) to oganesson (118) – have any real applications. They are too dangerous, too expensive or too scarce – many can only be created in tiny amounts.

Thulium (atomic number 69) was once the butt of scientific jokes and parody because for many years it was not considered to have any practical applications. However, a thulium laser is being developed within medical science for the treatment of cancer.

Extremely short-lived elements such as actinium (89) and astatine (85) are used only in research or to produce isotopes of other elements for medical purposes.

Protactinium (91) is listed between uranium and thorium, which both have numerous applications. But owing to its scarcity, high radioactivity and high toxicity, there are no known uses for protactinium. The most stable isotope of francium (87), francium-223, has a half-life of 22 minutes, which means it does not have a practical use.

The extremely rare berkelium (97) has no known practical applications.

The Periodic Table

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. Isotopes

Chemical elements can exist as two or more isotopes that have different numbers of neutrons in the nucleus. For example, while carbon always has six nuclear protons, it exists as three different naturally occurring isotopes with six, seven or eight neutrons. These isotopes are often written carbon-12, carbon-13 and carbon-14.

Chemically, different isotopes of an element are usually identical because their chemical properties are determined by their outer electrons. But different isotopes undergo nuclear decay at different rates. For instance, while most carbon on Earth is the stable isotope carbon-12, the isotope carbon-14 is radioactive and decays with a half-life of 5,700 years.

This underpins the technique of carbon dating. Constant interchange with the environment makes the ratio of carbon-14 to carbon-12 constant in a living tree, for instance, but the ratio drops with time in a predictable way after the tree dies. If ancient wood has just half the expected ‘living’ value of carbon-14, it must be about 5,700 years old.

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