---
title: "When was an element last added to the periodic table?"
description: "Nihonium, moscovium, tennessine and oganesson were named, completing row seven, 28 November 2016. What happened, and whether it plausibly could happen again."
url: https://atoneplace.net/the-last-time/new-element/
site: "At One Place"
---

# When was an element last added to the periodic table?

**When was an element last added to the periodic table?: 28 November 2016**

Nihonium, moscovium, tennessine and oganesson were named, completing row seven

Elements 113, 115, 117 and 118 were formally named in November 2016, filling the last gaps in the seventh row. All four are synthetic, produced a handful of atoms at a time, and decay within milliseconds — oganesson's longest-lived isotope has a half-life under a second. An eighth row would require element 119, which has been attempted and not achieved, and the difficulty rises steeply with each step.

- **What:** Nihonium, moscovium, tennessine and oganesson were named, completing row seven
- **When:** 28 November 2016
- **Category:** Science and measurement
- **Could this change?:** Yes. This streak could end, and if it does this page becomes a historical note rather than an answer.

## Science and measurement

| Question | When |
| --- | --- |
| When were the SI base units last redefined? | 20 May 2019 |
| When was the last leap second added? | 31 December 2016 |
| When did the number of planets last change? | 24 August 2006 |
| When was the metre last redefined? | 1983 |

> This page gives a date and never a "years ago". These pages are built as static files, so a computed interval would freeze at build time and quietly become wrong — which on a reference site is worse than making the reader do the subtraction.

## Common questions

### When was an element last added to the periodic table?

28 November 2016 — Nihonium, moscovium, tennessine and oganesson were named, completing row seven.

### What happened?

Elements 113, 115, 117 and 118 were formally named in November 2016, filling the last gaps in the seventh row. All four are synthetic, produced a handful of atoms at a time, and decay within milliseconds — oganesson's longest-lived isotope has a half-life under a second. An eighth row would require element 119, which has been attempted and not achieved, and the difficulty rises steeply with each step.

### Could it happen again?

Yes. This is one of the entries where the streak could plausibly end, which is stated on the page rather than left implied.

## Related pages

- [When were the SI base units last redefined?](https://atoneplace.net/the-last-time/si-base-units/)
- [When was the last leap second added?](https://atoneplace.net/the-last-time/leap-second/)
- [When did the number of planets last change?](https://atoneplace.net/the-last-time/planet-count/)
- [When was the metre last redefined?](https://atoneplace.net/the-last-time/metre-redefined/)
- [When was the last Boeing 747 delivered?](https://atoneplace.net/the-last-time/boeing-747/)
- [When did Microsoft Office last change its default font?](https://atoneplace.net/the-last-time/office-default-font/)
- [When did the London Underground last gain a line?](https://atoneplace.net/the-last-time/london-underground-line/)
- [When were the SI base units last redefined?](https://atoneplace.net/the-last-time/si-base-units/)
- [When was the last leap second added?](https://atoneplace.net/the-last-time/leap-second/)
- [When was the last VCR manufactured?](https://atoneplace.net/the-last-time/vcr/)
- [Everything, most recent first](https://atoneplace.net/the-last-time/)

## Sources

- Wikidata — Wikimedia Foundation (https://www.wikidata.org/) [CC0 1.0]