Nomenclature of Elements with Z > 100

Elements beyond $Z=100$ are not found in nature. They are synthesised one atom at a time by fusing lighter nuclei together in a particle accelerator, and the heaviest of them decay in milliseconds. Confirming that a genuinely new element has been made — as opposed to a contaminant or a mis-identified decay chain — requires independent replication, and only after that is IUPAC ready to approve a permanent name honouring a scientist, a place or a mythological figure. Until that day arrives, the element still needs to appear in papers, textbooks and databases, so IUPAC finalised a systematic naming rule in 1997 that needs nothing but the atomic number itself. The rule works digit by digit. Each of the ten digits $0$–$9$ maps to a fixed root and a one-letter abbreviation of that root, shown below.

Digit-to-root table

Reading $Z$ as a string of digits, replacing each digit by its root, concatenating the roots in the same order, and appending "-ium" gives the systematic name. Reading off the abbreviation of each root, in the same digit order, gives a three-letter symbol. This can be written as a simple correspondence:

where: $d_1 d_2 d_3$ are the digits of the atomic number in order, $R(d)$ is the root assigned to digit $d$ in the table, and $A(d)$ is that root's one-letter abbreviation. This is not a physical law but a bookkeeping map — every atomic number greater than 100 has exactly one systematic name, and every systematic name of this form decodes to exactly one atomic number, so the mapping runs cleanly in both directions. Two spelling points from the NCERT presentation are worth fixing early: when "bi" is followed by "nil" the two vowels are kept as written rather than merged (so $Z=112$ reads "unbibium", not a contracted form), and when "enn" is followed by "nil" the double "n" from the two roots is kept exactly as the table gives it (element 109, un + nil + enn + ium, is written "unnilennium" in the older NCERT convention). You are only expected to apply the table mechanically, not to invent further contraction rules of your own.

There is no formula to derive here — this is a naming convention, not a physical law — so the useful thing is to see why the rule is built this way rather than memorise it as an arbitrary trick.

It has to be unambiguous. A naming scheme used across every laboratory and journal in the world cannot rely on judgement calls. By fixing exactly one root and one abbreviation per digit, and by fixing the order (digits of $Z$, left to right), the mapping from $Z$ to name becomes purely mechanical — two chemists working independently, given the same $Z$, always produce the same name.

It has to be reversible. Because each root is distinct and none is a prefix of another (un, bi, tri, quad, pent, hex, sept, oct, enn, nil are all recognisably different once you know the list), a name can always be split back into its roots and hence its digits. This is why Worked Example 2 below can start from a name and recover $Z$ with no ambiguity — the rule was built to be read in both directions from the outset.

It has to scale indefinitely. Real elements beyond $Z=100$ have three-digit atomic numbers today, but the digit-by-digit scheme places no upper limit on $Z$: a four- or five-digit atomic number would simply add more roots to the chain. The rule needed to outlive any particular generation of discoveries, and a per-digit construction does that automatically.

It is deliberately temporary. The "-ium" ending marks the name as systematic rather than final — it signals to a reader that this is a placeholder, not a name chosen to honour a person or place. Once IUPAC confirms a discovery, the systematic name is retired in favour of a permanent one (element 101, systematically unnilunium under the old convention, is permanently mendelevium, Md, after Mendeléev). The systematic and permanent names are never both "correct" for the same purpose at the same time — the systematic name simply stops being used once approval arrives.

Question: Derive the IUPAC systematic name and symbol for the element with atomic number 114, and then, working the rule in the other direction, identify the atomic number and symbol for the systematic name "unniloctium."

Step 1. Take $Z = 114$ and write its digits in order: $1, 1, 4$.

Step 2. Convert each digit to its root using the table: $1 \to$ un, $1 \to$ un, $4 \to$ quad.

Step 3. Join the roots in digit order and append the suffix "-ium": un + un + quad + ium = ununquadium. Read off the first letter of each root's abbreviation in the same order, $1 \to$ u, $1 \to$ u, $4 \to$ q, giving the symbol Uuq. So element 114 is systematically ununquadium, Uuq (its confirmed permanent name is flerovium, Fl — quoted only for context, since deriving the permanent name is not part of this rule).

Step 4. Now reverse the process for "unniloctium." Split the name into recognisable roots by matching against the table: un-nil-oct-ium, giving un = 1, nil = 0, oct = 8.

Step 5. Read the digits in the order they appeared in the name to reconstruct $Z$: $1, 0, 8 \to Z = 108$. The symbol follows the same first-letter rule: un $\to$ u, nil $\to$ n, oct $\to$ o, giving symbol Uno.

Answer: $Z=114$ is ununquadium, symbol Uuq; the name unniloctium corresponds to $Z=108$, symbol Uno (permanent name hassium, Hs).

• Forgetting the "-ium" suffix, or wrongly attaching it to every root separately instead of once at the end of the whole joined string.
• Confusing similar-looking roots under exam pressure — especially $1=$un vs $9=$enn, and $4=$quad vs $5=$pent — always cross-check against the table rather than trusting memory.
• Building the symbol from the wrong letters, or using two letters instead of three: the rule takes exactly one letter from each of the three digit-abbreviations, in digit order, giving a three-letter symbol every time.
• Treating a systematic name as permanent, or writing both "ununquadium" and "flerovium" for $Z=114$ as if they were interchangeable current names — the systematic name is retired the moment IUPAC approves the permanent one.

Ask the tutor: want to practice converting a few more atomic numbers into systematic names, or decoding names back to Z — ask the AI tutor to quiz you.