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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 fluorine–fluorine bond of the difluorine molecule is relatively weak when compared to the bonds of heavier dihalogen molecules. 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 Be–F bond length is between 145 and 153 pm.The beryllium is sp 3 hybridized, leading to a longer bond than in BeF 2, where beryllium is sp hybridized. [11] In trifluoroberyllates, there are actually BeF 4 tetrahedra arranged in a triangle, so that three fluorine atoms are shared on two tetrahedra each, resulting in a formula of Be 3 F 9.
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. Ionic compounds lose their crystal lattice structure and break up into ions when dissolved in water or any other polar solvent. This process is called solvation.
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 carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is one of the strongest single bonds in chemistry (after the B–F single bond, Si–F single bond, and H–F single bond), and relatively short, due to its partial ionic character.
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]