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The main form of oxygen in the atmosphere is elemental oxygen
.
There are two allotropes of oxygen: oxygen O 2 and ozone O 3
1.
Oxygen
O 2 is a diatomic molecule, which is a colorless and odorless gas under normal temperature and pressure; it liquefies into a light blue liquid at 90K, and solidifies into a blue solid at 54K
.
O 2 is a non-polar molecule with 2 single electrons in the molecule, so the molecule has paramagnetism
O 2 has very little solubility in water, and it hydrates oxygen molecules in water
(O 2 ·H 2 O and O 2 ·2H 2 O) exist (Figure 11-1)
.
Figure 11-1 Schematic diagram of hydrated oxygen molecules
Oxygen has strong oxidizing ability in acidic and alkaline media
O 2 + 4H + + 4E - = 2H 2 O E [Theta] = 1.
23V
O 2 + 2H 2 O + 4E - = 4OH -E [Theta] = 0.
40V
At room temperature, the chemical properties of O 2 are not active; however, it can directly combine with most elements at high temperatures, and can also react with some reducing compounds
.
E.
The industry mainly uses fractionated liquefied air to prepare O 2
.
The most commonly used preparation method in the laboratory is to use MnO 2 to catalyze the decomposition of KCIO 3 , or heat to decompose oxygen-containing compounds
2.
Ozone
Ozone O 3 is a light blue gas with a fishy smell, and hence its name
.
In the O 3 molecule, the sp 2 hybridized central oxygen atom forms a σ bond with the two ligand oxygen atoms, which confirms the V-shaped configuration of the molecule (bond angle 117.
47°)
.
The p orbital of the central oxygen atom not participating in the hybridization overlaps with the p orbital containing a single electron in the ligand oxygen atom to form a delocalized x bond, as shown in Figure 11-2(a)
Discuss the use of molecular orbital theory O 3 molecules Ⅱ .
4 3 bond order
.
As shown in Figure 11-2(b), 3 atomic orbitals are combined to form 3 molecular orbitals, one of which is a bonding orbital (with energy lower than the atomic orbital), the other is an antibonding orbital (with energy higher than the atomic orbital), and There is a non-bonded orbital (the energy is the same as that of the atomic orbital)
Figure 1-20.
Delocalization and orbital energy level diagrams in molecules
It can be seen from the configuration of O 3 molecules that O 3 is a polar molecule and does not have paramagnetism
.
O .
3 melting, boiling point than O 2 , the solubility in water is higher than O 2 large
.
Ozone is highly oxidizing
Whether in acidic or alkaline solutions, ozone has strong oxidizing properties
.
There is a thin layer of ozone in the atmosphere at a distance of 25-40km from the ground
.
Ozone can absorb ultraviolet radiation from the sun, and it will react as follows to protect the animals and plants on the ground from being harmed.
O 3 =O 2 +O
The generated oxygen atoms can interact with O 2 molecules to regenerate O 3 , thereby completing the O 3 cycle
.
The discharge effect of thunderstorm weather will also convert a small amount of O 2 into O 3
.
In the laboratory, high-voltage discharge is mainly used to convert O 2 to O 3
.
Copiers and printers also produce a small amount of O 3 due to high-voltage discharge
.
Ozone is easily reduced by some reductive gases.
Pollution in the atmosphere makes the ozone layer thinner and thinner and can lead to holes in the ozone layer
.
