Structure
Its structure adopts the rhenium trioxide motif, featuring distorted AlF6 octahedra. Each fluoride is connected to two Al centers. Because of it is a 3-dimensional polymer, AlF3 has a higher melting point. In contrast, the other trihalides of aluminium, AlCl3, AlBr3, and AlI3, which are either molecular or 1-dimensional polymers, have low melting points and evaporate readily to give dimers. In the gas phase, at ca. 1000 °C, aluminium fluoride exists as trigonal molecules of D3h symmetry. The Al-F bond lengths of this gaseous molecule are 163 pm.
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“There is no such thing as a language, not if a language is anything like what many philosophers and linguists have supposed. There is therefore no such thing to be learned, mastered, or born with. We must give up the idea of a clearly defined shared structure which language-users acquire and then apply to cases.”
—Donald Davidson (b. 1917)
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