What Elements Are Named After Planets

Look at a periodic table long enough and the names start to feel like a map of human history. But there’s a whole subset that feels different — cosmic, almost. In practice, neptunium. You’ve got scientists (Einsteinium, Curium), places (Americium, Germanium), and mythological figures (Titanium, Promethium). Uranium. So mercury. Plutonium. They sound like a roll call of the solar system.

And that’s exactly what they are.

It’s not a coincidence. So the naming convention became a kind of celestial honor system. For a stretch of about 150 years, discovering a new planet and discovering a new element went hand in hand. But the list is shorter than most people think, and the stories behind them are messier than a textbook lets on.

What Elements Are Actually Named After Planets

Let’s get the list straight first. There are eight elements named after planets — or, more precisely, named after the Roman gods those planets were named after. The line blurs fast.

Mercury (Hg) — Element 80. Named for the fleet-footed messenger god. The planet Mercury got the name first; the element followed because it moves like liquid silver.
Venus — No element. There is no Venesium. The goddess has no atomic tribute.
Earth — No element named "Earthium" or "Terrium." We live here; we didn't name a metal after the dirt.
Mars — No element named after the god of war either. Iron (Fe) is the classic "Mars metal" in alchemy, but the modern name comes from Latin ferrum*.
Jupiter — No Jupitium. The king of gods got skipped.
Saturn — No Saturnium.
Uranium (U) — Element 92. Named for the planet Uranus, discovered just eight years earlier.
Neptunium (Np) — Element 93. Named for Neptune. The pattern holds.
Plutonium (Pu) — Element 94. Named for Pluto. At the time (1940), Pluto was the ninth planet. It still holds the name even after Pluto got demoted to dwarf planet status.

That’s it. Eight elements. Five planets (Mercury, Uranus, Neptune, Pluto, and arguably the Sun/Helios for Helium) have elemental namesakes. The rest of the solar system — Venus, Earth, Mars, Jupiter, Saturn — are absent from the table.

The Asteroid Connection

Here’s where it gets interesting. On the flip side, the gap between Mars and Jupiter? Because of that, it’s filled with asteroids. And those* got elements named after them.

Cerium (Ce) — Element 58. Named for Ceres, discovered in 1801. Ceres was considered a planet for about 50 years before being reclassified as an asteroid (and recently a dwarf planet).
Palladium (Pd) — Element 46. Named for Pallas, the second asteroid discovered (1802).

So if you count Ceres and Pallas as "planets" in the historical sense — which astronomers did at the time — the list grows. It’s a reminder that the periodic table is a fossil record of what we thought* the solar system looked like when each element was found.

Why This Naming Pattern Exists

It wasn't a formal rule. It was fashion. And nationalism. In practice, there was no International Union of Pure and Applied Chemistry (IUPAC) committee handing down edicts in 1789 or 1803. And a dash of ego.

In the late 18th and 19th centuries, astronomy was the prestige science. Day to day, discovering a planet made you famous across Europe. William Herschel found Uranus in 1781 and became an instant celebrity. Chemists, chasing their own kind of glory, borrowed that reflected light.

Naming a new element after the newest planet signaled: I am working at the frontier. My discovery is as significant as a new world.*

It also helped avoid fights. Because of that, naming an element after a person (like Davy or Berzelius) invited rivalry. Naming it after a country (Francium, Germanium, Polonium) invited political tension. But the planets? Plus, they belonged to everyone and no one. Neutral ground. Mythological, timeless, safe.

The Uranium Moment

Martin Heinrich Klaproth discovered uranium in 1789. Think about it: he named it Uran* (later Uranium) explicitly to honor Herschel’s planet. It was the first time an element was named after a celestial body since* antiquity (Mercury was known to the ancients, but the name is alchemical, not a "discovery" in the modern sense).

Klaproth didn't isolate pure uranium metal — that took another 50 years — but he identified the oxide in pitchblende. So the name stuck. It set the template.

How the Pattern Played Out: Step by Step

The sequence is almost poetic. Each new "planet" discovery triggered a race to name the next element.

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1. Uranus (1781) → Uranium (1789)

Herschel finds the first "new" planet in recorded history. Eight years later, Klaproth names his new element after it. The lag is short. The excitement is fresh.

2. Ceres (1801) → Cerium (1803)

Giuseppe Piazzi finds Ceres. It’s hailed as the missing planet between Mars and Jupiter. Two years later, Jöns Jacob Berzelius and Wilhelm Hisinger (independently, and simultaneously with Klaproth again) isolate cerium. They name it for the new world.

3. Pallas (1802) → Palladium (1803)

Heinrich Olbers finds Pallas months after Ceres. William Hyde Wollaston isolates palladium in 1803 and names it for the asteroid. Same year as cerium. The asteroid belt is pumping out element names.

4. Neptune (1846) → Neptunium (1940)

Here the pattern breaks. Neptune is found in 1846. But neptunium* doesn't appear until 1940.

Why the 94-year gap?

Because "neptunium" was claimed multiple times by mistake. In 1877, a chemist named Hermann claimed to find it in a mineral. He was wrong. Because of that, in 1898, another claim. Still, wrong again. The name "neptunium" became a ghost — a label attached to errors. But by the time Edwin McMillan and Philip Abelson actually* synthesized element 93 in a cyclotron at Berkeley, the name was available again. They took it. The planet connection was deliberate, a conscious callback to the uranium tradition.

5. Pluto (1930) → Plutonium (1940)

Clyde Tombaugh finds Pluto. Ten years later, Glenn Seaborg’s team at Berkeley creates element 94. They name it plutonium, following the sequence: Uranus → Uranium, Neptune → Neptunium, Pluto → Plutonium.

It’s the only time the naming happened before* the element was found in nature. Worth adding: plutonium is synthetic (trace amounts exist in uranium ores from neutron capture, but effectively it’s man-made). The planet name was a prediction, not a reaction.

Common Mistakes / What Most People Get Wrong

**Mistake: "Helium is

Mistake: "Helium is" named after the Sun, not a planet, and therefore does not belong to the planet‑element naming chain that began with Uranus. Helium’s name derives from Helios*, the Greek sun god, and was coined when the element was first detected in the solar spectrum during the 1868 eclipse. Because the Sun was already known to antiquity, the discovery did not trigger the same “new‑planet‑new‑element” excitement that later accompanied Uranus, Ceres, Pallas, Neptune, and Pluto. This means helium is often mistakenly cited as the first example of the celestial‑body naming tradition, when in fact it predates the pattern and follows an older mythological naming route.

Other frequent misunderstandings include:

Selenium and tellurium – Both names evoke the Moon (Selene*) and Earth (Tellus*), yet they were named not because these bodies were newly discovered but because the elements’ properties reminded early chemists of lunar and terrestrial characteristics. The Moon and Earth were already familiar, so no “planet‑discovery → element” lag exists.
Mercury – Although the element shares its name with the swift planet, the metal was known to alchemists long before the planet’s astronomical identity was solidified. The alchemical symbol (☿) predates modern astronomy, making mercury a holdover from antiquity rather than a product of the 18th‑century naming wave.
Synthetic elements beyond plutonium – After element 94, the practice of honoring newly discovered planets faded. Later transuranic elements received names tied to scientists, places, or poetic concepts (e.g., americium, curium, dubnium, oganesson). The shift reflects both the exhaustion of readily observable planets and the changing culture of element naming, which now prioritizes recognition of contributors over celestial homage.

These missteps reveal how the simple story of “planet → element” can be oversimplified. Consider this: the pattern worked best when a genuinely new celestial body entered public consciousness, sparking a timely chemical counterpart. When the heavenly object was already ancient, mythological, or when the element itself was synthetic, the naming logic diverged.

Conclusion

The tradition of naming elements after newly discovered planets illustrates a fascinating interplay between astronomy and chemistry in the late 18th and early 19th centuries. In real terms, from Uranus to Pluto, each planetary breakthrough inspired chemists to immortalize the discovery in the periodic table, creating a rhythmic cadence that lasted roughly a century and a half. That said, while the pattern eventually waned — due to misattributed claims, the synthetic nature of later elements, and evolving naming conventions — its legacy remains etched in the names of uranium, cerium, palladium, neptunium, and plutonium. Recognizing both the successes and the common misconceptions surrounding this tradition enriches our appreciation of how human curiosity about the heavens has repeatedly shaped the very language we use to describe matter.