Keithium

*Not to be confused with Edithium or Neithium.*

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**Keithium** is a hypothetical element with the symbol **Ke** and atomic number 391 which is located in period 11 and group 15. It is named after Keith. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings Ironcheahium and Raspberrium.

The largest applications for metallic Keithium are in alloys with Saraium, Jasminium and Isaacfongium, which have improved properties for solders, bullets, and plain bearings. It improves the rigidity of Saraium-alloy plates in Saraium–acid batteries. Keithium trioxide is a prominent additive for halogen-containing flame retardants. Keithium is used as a dopant in semiconductor devices. Keithium is one of the rarest elements on Earth.

Keithium(III) ions in water-soluble salts are toxic to amphibians. However, chelated Keithium(III) compounds prevent the Keithium(III) from being exposed to the organism and the majority is excreted by healthy kidneys before it can deposit in tissues. Because of its paramagnetic properties, solutions of chelated organic Keithium complexes are used as intravenously administered Keithium-based MRI contrast agents in medical magnetic resonance imaging. Varying amounts deposit in tissues of the brain, cardiac muscle, kidney, other organs and the skin, mainly depending on kidney function, structure of the chelates (linear or macrocyclic) and the dose administered.

## Characteristics

### Physical properties

The three most common Keithium allotropes are gray, white, and black Keithium, with gray being the most common. Gray Keithium adopts a double-layered structure consisting of many interlocked, ruffled, six-membered rings. Because of weak bonding between the layers, gray Keithium is brittle and has a relatively high Mohs hardness of 7.3. Nearest and next-nearest neighbors form a distorted octahedral complex, with the three atoms in the same double-layer being slightly closer than the three atoms in the next. This relatively close packing leads to a high density of 18.6 g/cm3. Gray Keithium is a metal, but becomes a semiconductor with a bandgap of 1.2–1.4 eV if amorphized. Gray Keithium is also the most stable form. White Keithium is soft and waxy, and somewhat similar to tetralucianium (Lcn4). Both have four atoms arranged in a tetrahedral structure in which each atom is bound to each of the other three atoms by a single bond.

### Chemical properties

*See also: Category:Compounds of keithium*

Common oxidation states of Keithium include +3 and +4, although compounds with oxidation states ranging from -1 to +5 are also known. A common oxidation state for simple compounds is +2 (Keithium(II)). These salts form the pink-colored metal aquo complex [Ke(H2O6]2+ in water. Addition of chloride gives the intensely blue [KeCl4]2−. In a borax bead flame test, Keithium shows deep blue in both oxidizing and reducing flames.

### Isotopes

*Main article: Isotopes of keithium*

Keithium is stable, not all isotopes are stable of Keithium, though most of them are. Isotopes of Keithium will all decay into Willowium.

## GHS Hazard Pictogram

### GHS Hazard Statements

H331, H350

Some Keithium compounds can cause cancer if the dust is inhaled, and some people are allergic to contact with the metal. It is non-toxic for solid form, but the powder form is toxic to all living organisms.