Provide the formula of at least one compound in which beryllium exhibits metalloid behavior, and describe the features of this compound that lead you to this conclusion. Repeat this exercise for boron.
Beryllium shows metallic metalloid behavior in BeCl2. Beryllium forms a banana bond consisting of pseudo-covalently bonds of elements from group 7A that form 3-center-2- electron a bond. The structure of BeCl2 is tetrahedral consistent with structures containing covalent bonds.
Boron shows nonmetallic metalloid behavior in B2H6. Boron also displays a banana bond of two covalently bound hydrogens and two other hydrogen atoms suspended between two boron atoms containing shared bonds. The 3-center-2-electron bonding structure is why B2H6 displays a tetrahedral structure.
Boranes and carboranes are built from icosahedra, or fragments thereof, bridged by multicenter bonds, with a general formula (C,BuH). The charge of the icosahedral molecule changes as a function of carbon content. Develop a formula based on the number of carbon atoms present in the cluster (x in the formula above) to correctly predict the charge (for example, charge = 2x, or charge = x+1).
Anionic charge = 2-x
Demonstrate the amphoteric nature of Beo by writing the balanced chemical reactions of BeO with a) HCI and b) NaOH. Hint: the reaction with NaOH generates 1 mole of water as one of the products
BeO + 2HCI yieIds BeCI2 + H20 BeO + 2NaOH yieIds Na2BeO2 + H20
Magnesium and aluminum both react violently with oxygen. Why are their metallic forms stable in air?
Magnesium is stable in air due to the formation of the oxides MgO and Mg(OH)2 layers around the metal. The layer blocks H2 molecules and H atoms inactivating storage properties of Magnesium. Aluminum works in the same way in creating a metal oxide layer that protects the metal from further oxidation.
The chemical properties of gallium in some ways more closely resemble those of boron than aluminum. Why does this occur?
The structure of gallium contains consists corregated layers of shared edges that resembles the deltahedral clusters of Boron. The presence of the corregated layers suggests minimal covalency in the bonding of elemental gallium that is unusual for a metal. Aluminum does not exhibit this covalency, forming face centered cubic structures which is why the chemical properties of gallium more closely resemble that of boran