Osmium and iridium tie for the top of the periodic table's heavyweight class, both packing over 22 grams into every cubic centimeter.
Quick answer: 1. Osmium, 2. Iridium, 3. Platinum, 4. Rhenium, 5. Neptunium, 6. Plutonium, 7. Gold, 8. Tungsten, 9. Uranium, 10. Tantalum.
Pick up a marble-sized lump of osmium and it weighs about as much as a golf ball made of lead — twice over. The densest metallic elements cram an extraordinary amount of mass into a tiny volume, a property driven by heavy atomic nuclei packed into tightly bound crystal structures. This list ranks the ten densest metallic elements by the density of the pure element in its standard solid phase. It's a who's-who of the platinum-group metals and the heavy actinides: osmium, iridium, and platinum lead a cluster of elements that all crowd near or above 19 g/cm3, with gold and tungsten running a near-photo-finish for the middle of the pack. For anyone curious about materials science, chemistry, or just what "heavy" really means at the atomic scale, these are the champions.
The densest naturally occurring element, edging out iridium by a razor-thin margin. RSC lists 22.5872 g/cm3 at 20 C, a title only settled in the 1990s once X-ray crystallography resolved the near-tie.
The second-densest element, sitting just ~0.12% below osmium (22.5622 vs 22.5872 g/cm3 per RSC). For over a century it vied with osmium for the crown before precise measurement broke the deadlock.
The third-densest element and the benchmark dense precious metal, with a CRC-standard density of about 21.45 g/cm3.
A transition metal with a CRC density of 21.02 g/cm3. It also boasts one of the highest melting points of any element, at 3186 C.
The densest actinide, a synthetic radioactive metal whose alpha phase reaches 20.45 g/cm3 near room temperature.
Its dense alpha phase measures about 19.82 g/cm3. Plutonium's density varies markedly by allotrope, so the alpha phase serves as the standard reference value.
At a standard 19.30 g/cm3, gold narrowly out-densifies tungsten and ranks as the densest of the common precious metals.
A CRC-standard 19.25 g/cm3 puts tungsten a hair below gold — close enough that RSC rounds both to 19.3. It also has the highest melting point of any metal, at 3422 C.
A dense actinide at about 19.05 g/cm3, best known for its nuclear applications.
At about 16.65 g/cm3, tantalum is the tenth-densest element and the densest one outside the ~19+ g/cm3 cluster of platinum-group metals and heavy actinides.
| # | Name | symbol | atomicNumber | category | meltingPointC |
|---|---|---|---|---|---|
| 1 | Osmium | Os | 76 | Platinum-group metal | 3033 |
| 2 | Iridium | Ir | 77 | Platinum-group metal | 2446 |
| 3 | Platinum | Pt | 78 | Platinum-group metal | 1768 |
| 4 | Rhenium | Re | 75 | Transition metal | 3186 |
| 5 | Neptunium | Np | 93 | Actinide | 644 |
| 6 | Plutonium | Pu | 94 | Actinide | 640 |
| 7 | Gold | Au | 79 | Transition metal | 1064 |
| 8 | Tungsten | W | 74 | Transition metal | 3422 |
| 9 | Uranium | U | 92 | Actinide | 1132 |
| 10 | Tantalum | Ta | 73 | Transition metal | 3017 |
Items are ranked by the density of the pure metallic element in grams per cubic centimeter (g/cm3) at or near room temperature (~20 C), using standard reference values from the Royal Society of Chemistry periodic table and the CRC Handbook of Chemistry and Physics. Highest density is rank 1. Inclusion criterion: naturally occurring or well-characterized metallic chemical elements with an established room-temperature density, measured for the pure element in its standard solid phase. For elements with multiple allotropes (e.g. neptunium, plutonium), the standard dense reference phase is used (alpha phase). Where reference sources round differently (RSC vs CRC), the more precise CRC-standard value is cited; osmium's edge over iridium was only confirmed via X-ray crystallography in the 1990s.
Osmium is the densest metal and the densest naturally occurring element, at about 22.59 g/cm3 (22.5872 g/cm3 per the Royal Society of Chemistry). Iridium is a very close second at about 22.56 g/cm3.
Osmium is denser, but only barely — about 22.5872 g/cm3 versus iridium's 22.5622 g/cm3 per RSC, a difference of roughly 0.12%. The two elements were long considered near-tied, and osmium's edge was only firmly established in the 1990s using X-ray crystallography.
Gold is very slightly denser than tungsten — about 19.30 g/cm3 versus 19.25 g/cm3 by CRC-standard values, close enough that RSC rounds both to 19.3. This near-match is why tungsten is sometimes used to counterfeit gold bars by weight.
Elements like osmium, iridium, and platinum combine heavy atomic nuclei with compact, tightly packed crystal structures, so a great deal of atomic mass fits into a small volume. That combination is what pushes them to the top of the density table, above even the heavy actinides.