Structure and Bonding
The structure of solid BeF2 resembles that of silicon dioxide. Be2+ centers are four coordinate and tetrahedral. Solid BeF2 adopts a number of polymeric structures analogous to those adopted by SiO2 namely α-quartz, β-quartz, crystobalite and tridymite, and its reactions with fluorides are quite analogous to the reactions of SiO2 with oxides. An analogy exists between BeF2 and AlF3: both adopt extended structures at mild temperature. BeF2 is considered to be highly covalent.
Gaseous BeF2 is found in the gas-phase above 1160 °C. Like the isoelectronic gases CO2 and SiO2, it is a linear molecule. The Be-F distance of 177 pm. The difference between the ambient temperature structures of BeF2 (rock-like solid) and CO2 (gas) reflects the low tendency of alkali metals to form multiple bonds.
BeF2 reaches a vapor pressure of 10 Pa at 686 °C, 100 Pa at 767 °C, 1 kilopascal at 869 °C, 10 kPa at 999 °C, and 100 kPa at 1172 °C.
Molten BeF2 resembles water in some ways, since it is a triatomic molecule with strong interactions via Be—F—Be bonds. As in water, the density of BeF2 decreases near its melting point. Liquid (molten) beryllium fluoride also has a fluctuating tetrahedral structure
Read more about this topic: Beryllium Fluoride
Famous quotes containing the words structure and, structure and/or bonding:
“One theme links together these new proposals for family policy—the idea that the family is exceedingly durable. Changes in structure and function and individual roles are not to be confused with the collapse of the family. Families remain more important in the lives of children than other institutions. Family ties are stronger and more vital than many of us imagine in the perennial atmosphere of crisis surrounding the subject.”
—Joseph Featherstone (20th century)
“Man is more disposed to domination than freedom; and a structure of dominion not only gladdens the eye of the master who rears and protects it, but even its servants are uplifted by the thought that they are members of a whole, which rises high above the life and strength of single generations.”
—Karl Wilhelm Von Humboldt (1767–1835)
“The bottom line on bonding with multiples seems to be that if you see bonding as a static event—a moment in time at which you must have eye contact and skin contact simultaneously with two or more infants—you may indeed be in trouble.”
—Pamela Patrick Novotny (20th century)