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The noble gases show extremely low chemical reactivity; consequently, only a few hundred noble gas compounds have been formed. Neutral compounds in which helium and neon are involved in chemical bonds have not been formed (although some helium-containing ions exist and there is some theoretical evidence for a few neutral helium-containing ones ...
Structure of a noble-gas atom caged within a buckminsterfullerene (C 60) molecule. Noble gases can also form endohedral fullerene compounds where the noble gas atom is trapped inside a fullerene molecule. In 1993, it was discovered that when C 60 is exposed to a pressure of around 3 bar of He or Ne, the complexes He@C 60 and Ne@C 60 are formed ...
Predicting the color of a compound can be extremely complicated. Some examples include: Cobalt chloride is pink or blue depending on the state of hydration (blue dry, pink with water) so it is used as a moisture indicator in silica gel. Zinc oxide is white, but at higher temperatures becomes yellow, returning to white as it cools.
Type II hydrates are formed by gases like O 2 and N 2. The unit cell of Type H consists of 34 water molecules, forming three types of cages – two small ones of different types, and one "huge". In this case, the unit cell consists of three small cages of type 5 12, two small ones of type 4 3 5 6 6 3 and one huge of type 5 12 6 8. The formation ...
Noble gases were not known in 1844 when this classification arrangement was published. Hydrogen, carbon, nitrogen and oxygen were grouped together on account of their occurrence in living things. Phosphorus, sulfur and selenium were characterised as being solid; volatile at an average temperature between 100 degrees and red heat; and ...
Several of the CPK colors refer mnemonically to colors of the pure elements or notable compound. For example, hydrogen is a colorless gas, carbon as charcoal, graphite or coke is black, sulfur powder is yellow, chlorine is a greenish gas, bromine is a dark red liquid, iodine in ether is violet, amorphous phosphorus is red, rust is dark orange-red, etc.
Liquid xenon has a high polarizability due to its large atomic volume, and thus is an excellent solvent. It can dissolve hydrocarbons, biological molecules, and even water. [54] Under the same conditions, the density of solid xenon, 3.640 g/cm 3, is greater than the average density of granite, 2.75 g/cm 3. [53]
Krypton is highly volatile and does not stay in solution in near-surface water, but 81 Kr has been used for dating old (50,000–800,000 years) groundwater. [25] 85 Kr is an inert radioactive noble gas with a half-life of 10.76 years.