Hey all why does the formula of aluminium oxide equate to Al2O3. Explain why the formula has two aluminium atoms for every three oxygen atoms?Thanks
Aluminum has 3 valence electrons and therefore form 3+ ion Oxygen receives 2 electrons to fill it's outer shell and form 2- ion. They can only be combined together when 2 Aluminum atoms producing 6+ charge (in total) joins with 3 Oxygen atoms producing 6- charge so that the overall charge on the new product Al2O3 is neutral.
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Its Al2 so you need to do 2 x 27 = 54 To work out this as a percentage of the whole divide 54/102 and x by 100 to give you the % You should get arround 53%
Aluminium oxide has the formula Al2O3 because in an ionic compound, in order to be neutral, the charges of each ion must be counteracted by the opposite charge. Al forms a 3+ ion and O forms a 2- ion. To make the charges match each other, with the smallest number of atoms possible, I look for the smallest common multiple of 2 and 3, which is 6. Therefore to cancel each other out, the Als must have a charge of 6+ and the Os must have have -6 charge. To make the charge of the Al 6+, I added a an Al atom to the formula = Al2 Then to make the charge of the O 6-, I added two Os, giving 3 O atoms. Hence my formula = Al2O3
The bonds in Al2O3 are about 45 percent covalent. The orbitals of aluminum and oxygen overlap to produce polar covalent bonds that extend into a network of aluminum and oxygen atoms. It is this network arrangement that accounts for the high melting point of the compound, about 2054 C. Aluminum has three valence electrons that it can share and oxygen has room in its p-orbital for two of them. The lowest ratio of aluminum to oxygen atoms in the solid network is therefore 2 to 3. The problem is that people often assume that metal/nonmetal compounds must contain ionic bonds, but in fact, no bond is completely (100 percent) ionic. Even the most ionic of bonds between cesium and fluorine is 8 percent covalent. In reality, all bonds in solids are covalent, some are just very, very polar, and it is these -- where the electronegativity difference is very high -- which we call ionic.
