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Beryllium fluoride has distinctive optical properties. In the form of fluoroberyllate glass, it has the lowest refractive index for a solid at room temperature of 1.275. Its dispersive power is the lowest for a solid at 0.0093, and the nonlinear coefficient is also the lowest at 2 × 10 −14.
The crystals can be formed by dissolving BeF 2 in water, adding HF and then glycine. When the solution is cooled triglycine tetrafluoroberyllate forms. Cs 2 BeF 4 and Tl 2 BeF 4 in the solution reduce growth on the 001 direction so that tabular shaped crystals of TGFB form. The thallium compound can cut growth on the 001 axis by 99%.
Lewis bases, such as the alkali fluorides, will donate fluoride ions to the beryllium, breaking the glassy bonds which increase viscosity. In FLiBe, beryllium fluoride is able to sequester two fluoride ions from two lithium fluorides in a liquid state, converting it into the tetrafluoroberyllate ion [BeF 4] 2−. [7]
Ionic bonds have high bond energy. Bond energy is the mean amount of energy required to break the bond in the gaseous state. Most ionic compounds exist in the form of a crystal structure, in which the ions occupy the corners of the crystal. Such a structure is called a crystal lattice.
The bond energy is significantly weaker than those of Cl 2 or Br 2 molecules and similar to the easily cleaved oxygen–oxygen bonds of peroxides or nitrogen–nitrogen bonds of hydrazines. [8] The covalent radius of fluorine of about 71 picometers found in F 2 molecules is significantly larger than that in other compounds because of this weak ...
Certain atoms, such as oxygen, will almost always set their two (or more) covalent bonds in non-collinear directions due to their electron configuration. Water (H 2 O) is an example of a bent molecule, as well as its analogues. The bond angle between the two hydrogen atoms is approximately 104.45°. [1]
[5]: 108 In alkoxides, oxygen forms a single bond with carbon and accepts an electron from a metal to form an alkoxide anion, R–O −, with three lone pairs. In oxonium ions, one of oxygen's two lone pairs is used to form a third covalent bond which generates a cation, >O + – or =O + – or ≡O +, with one lone pair remaining.
The polarity is due to the electronegativity of the atom of oxygen: oxygen is more electronegative than the atoms of hydrogen, so the electrons they share through the covalent bonds are more often close to oxygen rather than hydrogen. These are called polar covalent bonds, covalent bonds between atoms that thus become oppositely charged. [1]