Naming superheavy elements

Every atomic number beyond 100 is a superheavy element, and every one of them can be named the same mechanical way, without waiting for IUPAC's naming committee to rule on a permanent, honorific name. The system rests on two small building blocks.

A fixed root for every digit. IUPAC assigns each of the ten digits, 0 through 9, one short root:

These ten roots never change and must simply be memorised — they are the entire vocabulary of the scheme.

Reading the atomic number as separate digits. Any three-digit atomic number $Z$ (all superheavy elements known so far run from 101 to 118, and the scheme extends to any larger $Z$ synthesised later) can be split into its hundreds, tens and units digits:

where: $a$ is the hundreds digit, $b$ is the tens digit, and $c$ is the units digit of the atomic number, each an integer from 0 to 9 (with $a \geq 1$ for $Z > 100$). The naming rule takes each of $a$, $b$, $c$ in that left-to-right order, replaces it with its root from the table, concatenates the three roots, and appends "-ium" once at the very end — never after each individual root. The symbol is built the same way but shorter: take just the first letter of each of the three roots used and combine them into a three-letter symbol. So element 118 has digits $1, 1, 8$, giving roots un, un, oct, name ununoctium, symbol Uuo. This systematic name is a placeholder only — 118's ratified permanent name is oganesson (Og) — but constructing un-un-oct from 1-1-8 is exactly the mechanical skill being tested.

There is no formula to derive here — the rule is a labelling convention, not a physical law — but the reasoning behind it is worth stating plainly, because ISC examiners test the purpose as often as the mechanics. New superheavy elements are made one or a few atoms at a time in heavy-ion accelerators, and many decay within milliseconds. Confirming a discovery, and deciding which of several competing laboratories genuinely made the element first, can take IUPAC's evaluating committees years of scrutiny. Meanwhile, journals, textbooks and researchers still need to refer to element 104 or element 118 unambiguously in print. A name generated purely from the atomic number solves this: it needs no committee, cannot be disputed, and any chemist anywhere can construct or decode it from the ten roots alone. Once a discovery is verified and priority is settled, the discovering team is invited to propose a permanent name — often honouring a place, a scientist or a laboratory (rutherfordium for Ernest Rutherford, copernicium for Copernicus, moscovium for Moscow). That permanent name then replaces the systematic one everywhere, including on the periodic table itself. All of elements 101–118 now carry permanent names, yet the systematic rule stays firmly on the syllabus: it is a clean, self-contained algorithm, it demonstrates how a naming system can be built from first principles rather than convention, and it applies without modification to any element beyond 118 that is synthesised in the future.

Question. Construct the IUPAC systematic name and three-letter symbol for the element with atomic number 115. Then, decode the systematic name "ununseptium" back into its atomic number and symbol.

Step 1. Split $Z = 115$ into digits using $Z = 100a + 10b + c$: here $a = 1$, $b = 1$, $c = 5$, so the digits in order are 1, 1, 5.

Step 2. Look up each digit's root: $1 \to$ un, $1 \to$ un, $5 \to$ pent.

Step 3. Concatenate the roots in digit order and append "-ium" once: un + un + pent + ium = ununpentium. The symbol takes the first letter of each root used: u, u, p $\to$ Uup. (Element 115's confirmed permanent name is moscovium, symbol Mc.)

Step 4. Now decode "ununseptium" the reverse way: break it into roots by matching the root list — un + un + sept + "ium". Translate each root back to a digit: un $\to 1$, un $\to 1$, sept $\to 7$. Concatenating the digits in order gives $Z = 117$, and the symbol is the first letters u, u, s $\to$ Uus.

Answer: element 115 is systematically ununpentium, symbol Uup; and the name "ununseptium" decodes to $Z = 117$, symbol Uus. (Element 117's confirmed permanent name is tennessine, Ts.)

Competitive stretch

A question may give only the symbol, say "Uuh", and ask for the atomic number. Match each letter back to the root it starts: U $\to$ un (1), u $\to$ un (1), h $\to$ hex (6, the only listed root starting with h) — so $Z = 116$ (permanent name livermorium, Lv). Watch for letters that could start more than one root in principle; IUPAC's actual ten-root list happens to give each digit a unique starting letter, which is exactly why the three-letter symbol is always decodable without ambiguity.

• Reading the digits, or the roots, out of order — the concatenation always follows the atomic number left to right, most significant digit first.
• Confusing the temporary systematic name/symbol with the eventual permanent IUPAC name; a question may ask specifically for one or the other.
• Mixing up similar-sounding roots, especially "quad" (4) with "pent" (5), or "sept" (7) with "hex" (6) — these are memorised facts, not derivable from anything.
• Appending "-ium" after every root instead of once, at the very end of the full concatenated string.

Ask the tutor: if you want quick drills converting between atomic numbers and systematic element names and symbols, ask the AI tutor to quiz you both ways.