All practice pages/Interatomic theory/Elements
Element 76, a transition metal
The densest element found in nature, named for the smell of its toxic oxide.
Period 6, group 8. The other transition metals are tinted, and every cell opens its own article.
Osmium has 76 electrons, one for every proton, so the atom carries no charge. Below are the same 76 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d⁶ 6s²
Short form: [Xe] 4f¹⁴ 5d⁶ 6s², where [Xe] stands for the 54 electrons xenon already has.
That list runs by shell. In the order the subshells fill it reads [Xe] 6s² 4f¹⁴ 5d⁶, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Osmium sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones osmium can lose, gain or share, so they are the ones that decide what it bonds with.
Like other transition metals, osmium loses its outer s electrons, and often some d electrons as well, to form positive ions, and it can form more than one kind.
Among the rarest elements in the crust, found with platinum in ores from South Africa and Russia and in natural osmium-iridium alloys.
Smithson Tennant found it in 1803, together with iridium, in the black residue left after dissolving platinum ore in aqua regia. He named it from the Greek osme, smell, for the sharp odor of its volatile oxide.
Alloyed with iridium, its extreme hardness tipped fountain pen nibs, phonograph needles and instrument pivots. Osmium tetroxide stains fats for electron microscopes and was once used to reveal fingerprints.
Osmium tetroxide is highly toxic and evaporates easily, and its vapor damages the eyes and lungs. Finely powdered osmium slowly forms it in air.