The significance of oxygen to human existence cannot be emphasised.
Everyone is aware that without oxygen, life cannot be sustained for more than a few minutes. In addition to being essential for life, it is also utilised in many aspects of daily living.
How frequently have you seen astronauts monitoring the amount of oxygen that is available in their cylinders?
Almost all space movies feature a similar sequence, and to be honest, keeping people alive in space even in reality requires this. Understand why?
This is due to the fact that only the planet Earth has an atmosphere with a high enough concentration of oxygen to support life, and that oxygen is essential for human survival.
This is so that our bodies can breathe and the cells can make energy. Without oxygen, our cells cannot produce energy or perform any other essential tasks that are required to keep us alive. Thus, every cell in our body uses oxygen to oxidise glucose and produce energy.
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One of the most crucial elements in the atmosphere is oxygen. This element is necessary for the survival of all life on Earth, in its gaseous diatomic form. With an atomic mass of 8, oxygen is a member of group 16, period 2 of the current periodic table. It is the first chalcogen family member. Oxygen makes up 21% of the earth's atmosphere, and metals in their oxide forms make up more than 50% of the crust.
The chemical formula for oxygen is O2, and also called dioxygen. Oxygen forms a covalent bond with another oxygen atom. It is diatomic because it only needs two electrons to complete its octet, which it can get from another oxygen atom. Due to its electronegative nature, oxygen is very reactive.
Two double bonds between two oxygen atoms satisfy the Lewis structure of oxygen. Because there are lone pairs of electrons on both oxygen atoms, the O2 molecule is linear and has strong electronegativity and reactivity. The oxygen molecule can be written as O=O, and the covalent bond between the two atoms. The O2 molecule's bond length is 121 pm and its bond energy is 498 KJ mol-1.
When discovered in nature, a few chemical elements have the ability to exist in two or more different forms, or allotropes. Allotropy is a property that can be seen in elements like carbon, oxygen, phosphorus, tin, and sulphur.
The fact that the atoms are arranged differently into molecules or crystals explains the various physical characteristics displayed by an element's allotropes.An element's allotropes can vary in their chemical stability.
Dioxygen (O2) is the most prevalent allotrope of elemental oxygen.
Trioxygen (O3), also referred to as ozone and an extremely reactive allotrope of oxygen, is the next important allotrope. Ozone forms in the upper atmosphere when oxygen (O2) that has been split by ultraviolet (UV) radiation combined with atomic oxygen.
Group 16 of the periodic table is where oxygen is located. But unlike the other members of its family, oxygen exhibits some exceptional qualities because of some distinctive characteristics. In reality, oxygen's unusual properties are primarily caused by its-
i) small atomic radius,
ii) high electronegativity, and
iii) lack of vacant d-orbitals.
The peculiar characteristics of oxygen include the following:
Q1. Why does aluminium not undergo degradation in nature?
(A) It is an electronegative element
(B) It has an octet configuration
(C) It has a tough oxide layer
(D) It reacts at low temperature
Solution: An inert metal is aluminium. This means that when it forms naturally, it quickly reacts with airborne oxygen to form a strong, non-corrosive oxide layer. This layer prevents any other substance from reacting with aluminium metal.
Q2. What is carbon monoxide's nature?
(D) None of these
Solution: When carbon monoxide reacts with water, it does not exhibit acidic or basic properties. As a result, it is neutral oxide.
Q3. When heated, ammonium dichromate produces:
(A) Chromic oxide and nitrogen
(B) Chromic acid and ammonia
(C) Chromic acid and hydrogen
(D) All of these
Solution: Nitrogen gas and chromium oxide are released during the decomposition of ammonium dichromate when it is heated. The reaction is given below
Q4. Among the following, which cannot be an octatomic solid?
(D) None of the above
Solution: Other elements (S, Se, and Te) occur as octatomic solids while oxygen is a diatomic gas at ambient temperature. The oxygen atom forms a p-p double bond with another oxygen atom to create the O=O molecule because of its small size and strong electronegativity. At ambient temperature, oxygen exists as a diatomic gas because the van der Waals forces that attract the oxygen molecules are weak.
Q1. Why does sulphur exist as a solid while dioxygen exists as a gas
Answer: Because of the higher interelectronic repulsions in the smaller oxygen atoms, the O—O bond is significantly weaker than the S—S bond.
Additionally, oxygen forms multiple p-p bonds due to its larger electronegativity and smaller atomic radius. As a result, molecular oxygen exists as O2 molecules that are only loosely bound by van der Waals forces. As a result, at room temperature, it is a gas.
On the other hand, because of its larger radii, sulphur has a lower affinity to form p-p multiple bonds. Sulphur forms strong S—S single bonds because of its larger atomic size and low electronegativity, which accounts for its catenation property and causes it to exist as S8molecules with a puckered-ring structure. Sulphur is a solid as a result of this larger association, at room temperature.
Q2. Why is oxygen paramagnetic?
Answer: The paramagnetic properties of oxygen molecules could not be explained by the VBT(valence bond theory). The molecular orbital comes into play at this point. An oxygen atom's electronic configuration is 1s2 2s22p4 according to VBT(valence bond theory). According to VBT(valence bond theory), bonds are created by atomic orbitals; as a result, electrons are paired at the time of overlapping, making oxygen a diamagnetic species. However, according to experiment, oxygen molecules have a paramagnetic nature, which molecular orbital theory explains.
According to the MOT(molecular orbital theory), oxygen atoms overlapping atomic orbitals combine to form orbitals. The molecular orbital electronic configuration can be stated as
We can see that there are two electrons in the above-written electronic configuration, and they enter into two different pi degenerate orbitals. It is possible to describe the oxygen molecule as paramagnetic because it has two unpaired electrons. The two unpaired electrons in oxygen are the cause of its paramagnetic properties.
Q3. Why is Hydrogen sulphide (H2S) a gas and water (H2O) a liquid?
Answer: At room temperature, water is a liquid and hydrogen sulphide is a gas. because water has powerful hydrogen bonds due to oxygen’s high electronegativity. So, water has a high boiling point and is a liquid at normal temperature.
While the S-H bond is significantly less polar than the O-H bond and sulphur is less electronegative than oxygen. As a result, hydrogen sulphide is a gas and has no hydrogen bonds.
Q4. Kerosene oil is used to store sodium metals. Why?
Answer: Kerosene or dry mineral oil are used to store the sodium and potassium metals. These two metals belong to Group 1 of the periodic table. All of the metals in that category are highly reactive with water, including moisture in the air.
Due to its extreme reactivity, sodium and potassium react violently with the oxygen, carbon dioxide, and moisture in the air, potentially igniting a fire. Since sodium doesn't react with kerosene, it is kept submerged in it to stop this explosive reaction. These metals are shielded from any airborne moisture that could trigger a reaction in them that could be potentially violent.