118

In the United Kingdom, directory enquiry services moved in 2003 from the single number 192 to a competitive range beginning 118, each provider taking its own six-digit number. The change was intended to introduce competition and instead became a case study in it going wrong: prices rose sharply once callers could no longer tell the services apart, and Ofcom imposed a price cap on the range in 2019 after finding some calls costing more than twenty pounds.

Element 118 is oganesson (Og), named in 2016 for Yuri Oganessian, who led much of the work on superheavy elements at Dubna. It is one of only two elements named after a person who was alive at the time — seaborgium, for Glenn Seaborg in 1997, is the other. The element was first made in 2002 by bombarding californium with calcium ions; only a handful of atoms have ever existed, each lasting under a millisecond.

There are 118 elements on the periodic table (worldwide, as confirmed by IUPAC). Everything past 92 is made rather than found. Oganesson, element 118, has been produced a few atoms at a time and lasts under a millisecond.

The number of chemical elements confirmed is 118 (worldwide, IUPAC). Everything above 92 is synthetic and most of it decays in moments. The count is a fact about what has been made and confirmed, not about what can exist.

Oganesson sits at the foot of the noble gas column, but relativistic effects on electrons moving at a substantial fraction of the speed of light are predicted to make it behave quite unlike the gases above it — calculations suggest a solid at room temperature with significant chemical reactivity. The prediction cannot be tested, because too few atoms have ever existed and each survives under a millisecond. It is a case where the periodic table's own logic is expected to fail at its edge.

The periodic table is filled without gaps to element 118, and the heaviest few exist only as a handful of atoms surviving milliseconds. Anything beyond 118 would start a new period, and whether the table has a natural limit is unresolved.

118 is a semiprime — the product of two primes, 2 and 59 — and that is very nearly all its arithmetic has to say. It is not prime, not a power, not a member of any of the named sequences the catalogue tracks. Recording the absence matters on a page whose entire interest is chemical: a reader who arrives asking what is special about 118 should be told that the answer is the periodic table and not be offered a coincidence dressed up as a property.