The Science of Submontium

After some time, I’ve decided to write a brief post about why Submontium. First, I’d like to point out that Submontium is a theoretical element that fits perfectly into the game's setting. While it is fiction, it rests on the very solid foundations of real nuclear physics.

The name comes from the Latin Sub (under) and Mons (mountain). The game is set around the years 1895–1900. In the vicinity of Karlovy Vary, there is a mountain range called the Ore Mountains (Krušné hory), at the foot of which a meteorite containing a metal of entirely unique properties crashed in ancient times. Since we are already in the 21st century, I can afford to reveal a bit more about its closely guarded chemical background.

Submontium (symbol St) has an atomic number of 126. It is located in the eighth period of the periodic table and belongs to the so-called superactinides on the Island of Stability. Its electron configuration is [Og] 5g² 6f³ 7d¹ 8s² 8p¹. Yes, it opens the hyper-complex g-orbital.

Physical Properties

• Density: Extremely high (~25–30 g/cm³).
• State: Solid metal at room temperature.
• Appearance: Metallic luster, silvery-grey with a slight, unnatural bluish tint.
• Melting Point: 300–600 °C.
• Hardness: Brittle.
• Radiation & Emission: A strong alpha emitter with a long half-life. It reliably ionizes the surrounding air, causing a faint bluish glow around the sample itself.
• Magnetism: Strongly paramagnetic.
• Crystal Structure: Hexagonally complex crystal lattice with exceptionally high density.

Chemical Reactivity

• Oxidation States: Typically +3, +4, +5, +6, exceptionally up to +8. Thanks to its active 5g, 6f, and 7d electrons, it possesses extremely rich chemistry.
• Reactivity: Moderately reactive. Relativistic effects acting on the 8s/8p electrons make it chemically more stable than lighter superactinides.
• Compounds: Forms oxides (StO₂, StO₃), halides (e.g., gaseous StF₆, or StCl₃ · 6H₂O), and carbides (complex salts like StWC₂). Its chemistry resembles a combination of actinides and tungsten or uranium, but with a specific "g-orbital twist".
• Reaction with Water: Likely a violent reaction producing hydroxide and releasing hydrogen gas, similar to classical actinides.
• Color of Compounds: A highly unique property. Due to the 5g electrons, it forms compounds with unusual, exotic colors, most often purple, turquoise, or pearlescent.