Nomenclature of Elements with Atomic Numbers >100
NCERT Reference: Chapter 3 – Classification of Elements and Periodicity in Properties, Page 87
Quick Notes
- Elements beyond atomic number 100 are usually synthetic and unstable.
- Naming them avoids confusion until their discovery is confirmed and a permanent name is assigned.
- IUPAC naming system uses:
- Numerical roots for each digit of the atomic number
- Suffix ‘-ium’
- Example Element 110 → Un-un-nilium (Uun)
- Symbol is created by taking the first letter of each root.
Full Notes
Elements with atomic numbers greater than 100 are either synthetic (man-made) or have only recently been discovered. These elements often:
- Exist for very short times
- Lack clearly verified properties
- Are discovered by different research groups around the world
To avoid confusion or disputes over naming, the International Union of Pure and Applied Chemistry (IUPAC) developed a systematic method for temporary naming.
IUPAC Rules for Naming Elements with Z > 100
The system is based on numerical roots derived from the atomic number. Here's how it works:
- Use roots for each digit of the atomic number (see table below).
- Combine the roots in order of digits.
- Add the suffix “-ium” at the end.
- Omit repetitive letters like double "i" (e.g., "biium" becomes "bium").
- Form the symbol using the first letter of each root, capitalizing the first letter only.
| Digit | Root |
|---|---|
| 0 | nil |
| 1 | un |
| 2 | bi |
| 3 | tri |
| 4 | quad |
| 5 | pent |
| 6 | hex |
| 7 | sept |
| 8 | oct |
| 9 | enn |
Examples
Example Element 110
Digits: 1–1–0 → un-un-nil
Add suffix: Ununnilium
Symbol: Uun
Example Element 118
Digits: 1–1–8 → un-un-oct
Add suffix: Ununoctium
Symbol: Uuo
Example Element 124
Digits: 1–2–4 → un-bi-quad
Add suffix: Unbiquadium
Symbol: Ubq
Purpose of the System
This nomenclature is meant to be temporary, being used until:
- The element is officially discovered
- Priority is confirmed by IUPAC
- A permanent name is proposed (often honoring a scientist, place, or property)
Once the name is approved, it replaces the temporary name.
Summary
- IUPAC developed a naming system for elements with atomic numbers above 100 to maintain clarity and avoid disputes.
- Temporary names are based on combining numerical roots and the suffix “-ium”.
- The system remains in place until the discovery and official naming of the element are confirmed.