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1.
Aluminum element
Elemental aluminum is extracted from bauxite Al 2 O 3 which is widely distributed in nature
.
Utilizing the amphoteric nature of Al 2 O 3 , use alkali to convert the insoluble Al 2 O 3 into soluble Na[Al(OH) 4 ]; after filtering out the insoluble impurities, turn to Na[Al(OH) 4 ] solution CO 2 is passed through to obtain Al(OH) 3 precipitation; Al(OH) 3 is sintered to obtain purer Al 2 O 3
Metal aluminum is very lively, but it is easy to form a dense protective film on the aluminum surface that has been placed in the air for a long time, which prevents aluminum from being corroded.
Therefore, aluminum utensils have been widely used in daily life
Aluminum is an amphoteric metal, which can react with acid or alkali
Metal aluminum has strong reducibility and can replace metal from many transition metal oxides (such as Fe 2 O 3 , Cr 2 O 3 , MnO).
This is mainly due to the fact that the formation reaction of Al 2 O 3 can release a lot of heat.
2.
Oxygen compounds of aluminum
Alumina includes two types
.
The commonly referred to as amphoteric oxide Al 2 O 3 refers to γ-Al 2 O 3
Of Al 2 O .
3 of another polymorph is-A of Al 2 O .
Al(OH) 3 is an amphoteric substance, which can be dissolved in acid or alkali
.
However, Al(OH) 3 cannot be dissolved in ammonia water.
This property can realize the separation of Al 3+ from some metal ions soluble in ammonia water
3.
Aluminum halides
AIF 3 is an ionic compound, and the coordination number of Al 3+ is 6
.
The AlCl 3 crystal is an ionic compound, and the coordination number of Al 3+ is 6
In the AlCl 3 dimer, Al adopts sp 3 hybridization
.
The two single-electron hybrid orbitals of each Al and the two Cl p-orbitals with single electrons "head-to-head" form
.
Key
.
The 2 Al centers and the 4 ends Cl are on the same plane
.
In addition, 2 bridges Cl are located on both sides of the plane, and are shared by 2 Al to form a Cl bridge; C1 bridge provides a single-electron orbital and an electron-paired orbital to form a triple-center bond with 2 Al.
Al provides an electron, and the Al-CI-Al bond forms a three-center four-electron bond
.
It can also be seen that the Cl bridge forms a covalent bond and a coordinate bond with two Al centers, which is different from the hydrogen bridge in C 2 H 6
.
The main reason that AlCl 3 forms a dimeric structure is also caused by the lack of electrons in aluminum
.
Figure 13-18 Dimerization structure of ACl3
Related link: The similarity of boron and silicon
