How can the periodic table be used to predict the properties of the elements?
Creating new elements is not a simple process. Scientists use a particle accelerator to smash light atoms into a thin metallic foil that contains heavier atoms. They hope that the two nuclei at the centre of these atoms will fuse and form a heavier nucleus.
When these heavy elements form, they are usually highly unstable. They decay so quickly that we don’t usually see the element itself. Instead, we see a decay product. In that respect, even new elements aren't always 'discovered' directly. In some cases, scientists haven’t synthesized enough of the element for us to know what the element even looks like! Nevertheless, we consider the elements as known. We name them and list them the periodic table.
For example, in 2003, scientists first observed element 115 (ununpentium, Uup) They bombarded americium-243 with calcium-248 ions and produced four atoms of Uup, which lived for less than one fifth of a second.
₂₀ ⁴⁸Ca + ₉₅²⁴³Am → ₁₁₅²⁸⁸Uup + 3 ₀¹n
It took until September 2013 for the discovery to be confirmed, and about 50 atoms have been synthesized to date.
We can predict the properties of Uup because the Periodic Table organizes elements according to their atomic number.
Uup appears below bismuth in Group 15 of the Periodic Table. Its outermost electron configuration is 7s²7p³. P, As, and Sb all form compounds with oxidation states of +5 and +3. Bi tends to form only +3 compounds because of a phenomenon called the “inert pair effect”. We predict that Uup will continue this trend and form only +3 and +1 oxidation states. Nitrogen(I) and bismuth(I) are known but rare, but ununpentium(I) may be more stable. Element 114 (flerovium) appears to have noble gas-like properties. If this is the case, ununpentium will likely form +1 cations, since Uup+ will have the same electron configuration as flerovium.