Why does IUPAC use a systematic nomenclature for elements with Z greater than 100 at all?

The naming of a new element is traditionally the privilege of its discoverer, ratified by IUPAC. For very heavy elements only a few atoms can be made, so rival laboratories sometimes claimed the same element before the discovery was confirmed — for example, the Americans called element 104 Rutherfordium while the Soviets called it Kurchatovium. To avoid such disputes IUPAC ruled that, until a discovery is proved and an official name is recognised, the element carries a provisional name derived directly from its atomic number using fixed numerical roots.

What are the numerical roots used in IUPAC systematic nomenclature?

The roots for digits 0 to 9 are: nil (0), un (1), bi (2), tri (3), quad (4), pent (5), hex (6), sept (7), oct (8) and enn (9). Their one-letter abbreviations are n, u, b, t, q, p, h, s, o and e respectively. The roots are written in the order of the digits of the atomic number and the suffix -ium is added at the end.

How do I build the IUPAC systematic name and symbol from the atomic number?

Split the atomic number into its individual digits, replace each digit with its numerical root, write the roots in the same order, and add -ium. The three-letter symbol is formed from the first letter of each root, capitalised only at the start. For example Z = 104 gives un + nil + quad + ium = Unnilquadium, symbol Unq; Z = 120 gives un + bi + nil + ium = Unbinilium, symbol Ubn.

What are the drop-rules for the letters n and i in these names?

Two euphony rules tidy up the spelling. First, the final n of enn is dropped when it is immediately followed by nil — so enn + nil becomes ennil, not ennnil. Second, the final i of bi or tri is dropped when it is immediately followed by the suffix -ium — so a name ending in bi or tri before ium loses that i. These rules affect only spelling, never the symbol.

What is the IUPAC name of the element with atomic number 119?

The digits of 119 are 1, 1 and 9, whose roots are un, un and enn. Writing them in order and adding -ium gives Ununennium, with the three-letter symbol Uue. This was the answer to NEET 2022.

Do elements such as Unnilquadium and Ununoctium still carry these systematic names today?

No. All elements up to atomic number 118 have now been discovered and have received permanent IUPAC names. The systematic placeholders have been replaced by official names — for instance Unnilquadium (Z = 104) is now Rutherfordium, Unnilhexium (Z = 106) is Seaborgium, Unununnium (Z = 111) is Roentgenium, and Ununoctium (Z = 118) is Oganesson. The systematic system is still used only for elements that have not yet been confirmed, such as Z = 119 and above.

Nomenclature of Elements with Z > 100 — NEET Chemistry

Why a systematic naming scheme exists

The naming of a new element has traditionally been the privilege of its discoverer, with the suggested name later ratified by IUPAC. For the very heavy elements this tradition broke down. Elements with very high atomic numbers are so unstable that only minute quantities — sometimes only a few atoms — are ever obtained, and their synthesis demands sophisticated, costly equipment available in only a handful of competing laboratories worldwide.

In that competitive climate, scientists were sometimes tempted to claim a discovery before reliable data had been collected. The classic example given in NCERT is element 104: American scientists named it Rutherfordium, while Soviet scientists named the same element Kurchatovium. With two names attached to one unconfirmed element, the literature became confused.

To resolve such disputes, IUPAC recommended that until a new element's discovery is proved and its name officially recognised, the element shall carry a systematic name derived directly from its atomic number, using fixed numerical roots for the digits 0 to 9.

This gives every undiscovered or unconfirmed element an unambiguous placeholder that any chemist can decode without controversy. Once the discovery is confirmed, the element receives a permanent name and symbol by a vote of IUPAC representatives — a name that may honour the country or state of discovery or a notable scientist. The systematic name then quietly retires.

The numerical roots (0–9)

The entire scheme rests on ten numerical roots, one for each decimal digit, together with a one-letter abbreviation used to build the symbol. These are reproduced from NCERT Table 3.4 below. Memorising this table — both the spelling of each root and its first letter — is the single most important step, because every name and symbol is assembled from it.

Digit	Root	Abbreviation
0	nil	`n`
1	un	`u`
2	bi	`b`
3	tri	`t`
4	quad	`q`
5	pent	`p`
6	hex	`h`
7	sept	`s`
8	oct	`o`
9	enn	`e`

Two abbreviations are worth a second glance because they are easy to confuse. The root for 4, quad, abbreviates to q — not k. The root for 5, pent, abbreviates to p; do not let the spelling of "pent" tempt you toward anything else. With these ten rows fixed in memory, the rest of the topic is pure procedure.

Rules for building name and symbol

The procedure NCERT prescribes is short and entirely mechanical. The roots are put together in the order of the digits that make up the atomic number, and the suffix -ium is added at the end to give the name. The symbol is then read off from the first letters of those same roots.

Step	What you do	Result for Z = 102
1	Write the atomic number digit by digit	1 · 0 · 2
2	Replace each digit with its root	un · nil · bi
3	Join the roots in order, add the suffix -ium	Unnilbium
4	Take the first letter of each root for the symbol	u · n · b → Unb
5	Capitalise only the first letter of the symbol	Unb

Notice that the symbol always has exactly three letters, one per digit of the atomic number, regardless of how long the spelled-out name turns out to be. The suffix -ium contributes to the name but never to the symbol. The schematic below traces this assembly visually.

Figure 1

Figure 1. Root-to-name assembly for Z = 104. Each digit maps to one root; the roots are concatenated in order and capped with the suffix -ium, while the first letter of each root gives the three-letter symbol Unq.

The two drop-rules: n and i

Two small spelling rules tidy the names so they read smoothly. These are euphony adjustments only — they change the spelling of the name but never the symbol, which is always built directly from the unmodified first letters.

Rule	Trigger	Example
Drop the final n of enn	when immediately followed by nil (the root for 0)	enn + nil → ennil (not ennnil)
Drop the final i of bi or tri	when immediately followed by the suffix -ium	…bi + ium → …bium; …tri + ium → …trium

The first rule prevents an awkward triple-n; it bites only when a 9 is followed by a 0. The second rule prevents the clumsy endings "biium" and "triium": whenever the last digit of the atomic number is a 2 or a 3, the name ends in -bium or -trium rather than -biium or -triium. Both are reflected in the standard NCERT table, so if you build a name and it disagrees with the table, a missed drop-rule is the usual culprit.

NEET Trap

The drop-rules touch the name, not the symbol

Students who memorise "Unnilbium → Unb" sometimes try to apply the same dropping logic to the symbol. Do not. The symbol is read straight from the first letters of the original roots (u, n, b). The dropped letters in Unnilbium (the i of bi) and in Ununennium are interior to the name only.

Build the symbol from the raw root initials first; apply the n- and i-drops only to the spelled-out name.

Worked derivations from Z

With the roots and rules fixed, every question becomes a three-line exercise: split, substitute, suffix. The examples below cover the cases NEET favours — a clean four-digit-free element, an element exercising the i-drop, and an element above 118 that still legitimately carries a systematic name.

Example 1 · Z = 104

Derive the IUPAC systematic name and symbol.

Digits 1, 0, 4 → roots un, nil, quad. Join and add -ium: Unnilquadium. Symbol from first letters u, n, q → Unq. No drop-rule applies here.

Example 2 · Z = 120

Derive the IUPAC systematic name and symbol.

Digits 1, 2, 0 → roots un, bi, nil. The final root nil does not abut enn, so the n-drop does not apply; the i of bi does not abut -ium (a nil sits between), so the i-drop does not apply either. Join and add -ium: Unbinilium. Symbol u, b, n → Ubn. This is exactly NCERT's Problem 3.1.

Example 3 · Z = 113

Derive the IUPAC systematic name and symbol, watching the suffix.

Digits 1, 1, 3 → roots un, un, tri. The last digit is 3, so the i of tri abuts -ium and is dropped: tri + ium → trium. Name: Ununtrium. Symbol u, u, t → Uut. (This element is now officially Nihonium, Nh.)

Example 4 · Z = 119

Derive the IUPAC systematic name and symbol.

Digits 1, 1, 9 → roots un, un, enn. The enn is followed by the suffix -ium, not by nil, so the n-drop does not fire. Join and add -ium: Ununennium. Symbol u, u, e → Uue. This was the answer to NEET 2022.

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Keep going

Once you can name a superheavy element, see where it sits: explore the s-, p-, d- and f-blocks to place Z > 100 elements in the periodic table.

Systematic to official names: Z = 101–118

NCERT Table 3.5 lists, for every element from Z = 101 to 118, both the IUPAC systematic name (with its three-letter symbol) and the official name and symbol the element now carries. NEET examiners draw on this table directly — matching a systematic name to its official name, or asking for the symbol of a given atomic number. The complete mapping is reproduced below.

Z	Systematic name	Sym.	Official name	Sym.
101	Unnilunium	`Unu`	Mendelevium	`Md`
102	Unnilbium	`Unb`	Nobelium	`No`
103	Unniltrium	`Unt`	Lawrencium	`Lr`
104	Unnilquadium	`Unq`	Rutherfordium	`Rf`
105	Unnilpentium	`Unp`	Dubnium	`Db`
106	Unnilhexium	`Unh`	Seaborgium	`Sg`
107	Unnilseptium	`Uns`	Bohrium	`Bh`
108	Unniloctium	`Uno`	Hassium	`Hs`
109	Unnilennium	`Une`	Meitnerium	`Mt`
110	Ununnillium	`Uun`	Darmstadtium	`Ds`
111	Unununnium	`Uuu`	Roentgenium	`Rg`
112	Ununbium	`Uub`	Copernicium	`Cn`
113	Ununtrium	`Uut`	Nihonium	`Nh`
114	Ununquadium	`Uuq`	Flerovium	`Fl`
115	Ununpentium	`Uup`	Moscovium	`Mc`
116	Ununhexium	`Uuh`	Livermorium	`Lv`
117	Ununseptium	`Uus`	Tennessine	`Ts`
118	Ununoctium	`Uuo`	Oganesson	`Og`

Two rows are worth pinning down because they reward a careful reading of the n-drop. For Z = 109, enn (9) is followed directly by -ium, so the name is Unnilennium with no extra drop. For Z = 110, the digits are 1, 1, 0 → un, un, nil — the second un abuts nil with no clash, giving Ununnillium. The pair Unnilennium (109) and Ununnillium (110) are deliberately similar on the page and are a favourite swap in matching questions.

Figure 2

Figure 2. The life-cycle of a superheavy element's name: a disputed synthesis is given an unambiguous systematic placeholder built from its atomic number, which is later replaced by a ratified official name once the discovery is confirmed.

NEET Trap

Z = 111 is Roentgenium, not Darmstadtium

NEET 2020 set a matching question whose distractor paired Unununnium (Z = 111) with Darmstadtium. Darmstadtium (Ds) is Z = 110; Z = 111 is Roentgenium (Rg). Anchor the order Darmstadtium-110, Roentgenium-111, Copernicium-112 and the trap collapses.

110 Ds · 111 Rg · 112 Cn — keep these three adjacent rows memorised as a block.

Beyond Z = 118: names still in use

As of now, elements with atomic numbers up to 118 have all been discovered and have received official IUPAC names, so for those the systematic names are purely historical. Where the scheme is still actively used is for elements that have not yet been confirmed — atomic number 119 and beyond. These genuinely carry their systematic names today.

Z	Digits → roots	Systematic name	Symbol
119	1·1·9 → un·un·enn	Ununennium	`Uue`
120	1·2·0 → un·bi·nil	Unbinilium	`Ubn`
121	1·2·1 → un·bi·un	Unbiunium	`Ubu`
122	1·2·2 → un·bi·bi	Unbibium	`Ubb`
123	1·2·3 → un·bi·tri	Unbitrium	`Ubt`

For Z = 122 the i-drop fires on the final bi (it abuts -ium), giving Unbibium; for Z = 123 it fires on the final tri, giving Unbitrium. These five rows show the scheme has no upper limit — it can name an element of any conceivable atomic number, which is precisely why IUPAC adopted it as the universal default until a permanent name is ratified.

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