Oxygen is a diatomic molecule with a bond angle of 180 degrees. It is a colorless, odorless, and tasteless gas. It is not a combustible gas but helps in the combustion of other materials.
Chemical Reactivities of O2
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It has high chemical reactivity, and it readily forms oxides when reacting with other elements and compounds.
We rely on plant photosynthesis to provide molecular O2 in the atmosphere. Furthermore, atmospheric O2 levels would collapse to near zero if photosynthesis were to stop.
Properties of O2
Physical Properties
| Name of molecule | Oxygen |
| Chemical formula | O2 |
| Molar mass | 32.00 g/mol[3] |
| Bond angle | 180 |
| Polarity | Nonpolar |
| Molecular geometry | Linear |
| No. of valence electrons | 12 |
Chemical Properties
| Boiling point | -183°C |
| Melting point | -219°C |
| Ionization Energy | very high |
| Metallic character | low |
Uses of Oxygen
Some of the essential uses are mentioned below:
Life Supporting
It is vital for life as it is essential for breathing.
Industrial Use
- As a compressed gas, it is used for cutting and welding metals
- Used as oxidizers in rocket engines.
- During the smelting process, it eliminates sulfur and carbon impurities.
- Much chemical feedstock, such as ethylene oxide, requires oxygen to be produced.
Medical Use
- It is essential medically because animals (including humans) breathe molecular O2 and require it for metabolism.
- Its molecular form is used in oxygen treatment and hyperbaric chambers for therapeutic purposes and breathing gas for space exploration and SCUBA diving.
- Its cylinders are used in hospitals when a person faces difficulty in breathing.
- Used as a fuel
- Act as a life support system for scuba divers, submarines, etc.
Uses in Body
- In the body, it’s being consumed in a variety of ways.
- It is a required chemical element in the body of any animal or plant.
- Two metalloproteins carry it out in human bodies: hemoglobin and myoglobin.
- Hemocyanins and hemerythrin are two more dioxygen transport proteins besides hemoglobin and myoglobin.
- Marine invertebrates contain hemerythrin.
- The blood volume of a human is around 5 liters. Each blood cell contains 0.25 million hemoglobin molecules, and each milliliter of blood contains 5000 million blood cells.
Oxygen in Blood Transportation
- Hemoglobin is needed for the transport of it throughout our bodies.
- Myoglobin is involved in the storage and utilization of oxygen in muscular tissues.
- Many molecules in the metabolic chain are biosynthesized with it in our bodies.
- It changes some lipid-soluble molecules into water-soluble compounds that can be excreted.
Allotropic Forms of Oxygen
Ozone
Another type of it is ozone. It forms in the stratosphere of the earth. Oxygen molecules are divided into single atoms by ultraviolet radiation (UV). O3 is formed when single atoms of oxygen attach to O2 molecules. Because there is more UV in the stratosphere, the concentrations of O3 are higher. The ozone layer blocks UV, making it harder for O2 molecules to split in the lower atmosphere (troposphere), where we dwell. When O2 is exposed to extreme heat and pressure, ozone can still develop in the troposphere.
Liquid Oxygen
When we cool it to 183°C, it turns into a liquid Rockets, such as the Rocket Lab’s Electron rocket, employs liquid O2 as a propellant
Solid Oxygen
At temperatures below 218.79°C, O2 solidifies. The substances are transparent with a bright sky-blue color in both their liquid and solid phases.
Structure of O2
Molecular Geometry of O2
- It is the diatomic molecule with linear geometry having 180 degrees bonds between atoms.
- Both atoms in oxygen molecules have similar electronegativity and share the same ratio of electrons that’s why they are nonpolar.
Lewis Structure
A Lewis structure is a molecule’s structural representation in which dots represent electron positions surrounding the atoms and lines or dot pairs represent covalent bonds. The aim of designing a Lewis dot structure is to help in detecting chemical bond formation by identifying lone electron pairs in molecules.
Lewis structures can be created for molecules with covalent bonds and coordination compounds. The reason for this is that in a covalent link, electrons are shared. It’s more like one atom transfers an electron to the other in an ionic relationship.
Importance of Lewis Structure
- The Lewis structure is a diagrammatic description of the formation of bonds between molecules.
- This structure also helps in predicting the number of lone electrons present in the molecule and how they will behave in a bond formation.
- Bonds are represented by lines, and lone pairs of electrons are represented by dots in this diagram.
- The Lewis structure better explains the distribution of electrons within a chemical as well as its molecular shape.
Construction of the Lewis Structure
When developing the Lewis structure of the Oxygen molecule, the following steps must be followed:
Step 1: Determine the valence electrons of each atom.
To construct the Lewis structure of an oxygen molecule, we must first determine the valence electrons that exist in individual oxygen atoms, as illustrated in the diagram below: Following steps must be followed while constructing the Lewis structure of the Oxygen molecule:
| Atom | Electronic configuration | Valence electrons |
| 😯 | 1s2, 2S2, 2p4 | 6 |
Electrons in the valence shell of the O2 molecule.
Valence electrons in O2: 6+6
Step 2: Electron Pairs are Generated Between the Atoms
According to Lewis’s structure, there are twelve spots of electrons in oxygen molecules. Six electrons surround each oxygen atom. This figure shows six electrons present in the valence shell of an O2 atom. Four electrons from both atoms are shared, and a double bond is formed between the two atoms.
Step 3: Centre Atom of O2 Molecules
Because there are only two atoms, and they are both O2, there is no need to worry about choosing the center atom.
Step 4: Identifying Lone Pairs on Atoms
- We can start identifying lone pairs of atoms after establishing the central atom and drawing the O2 molecule.
- It’s important to remember that there are six electron pairs overall.
- In the drawn sketch, there is already a bond.
- On oxygen, there are still five lone pairs to mark.
- We can designate residual lone pairs on both oxygen atoms because there isn’t a central atom.
- One oxygen atom takes three lone pairs, while the remaining one takes two lone pairs.
- Both oxygen atoms now have their valence electron pairs.
Step 5: Mark Charges on Atoms
On both O2 atoms, there exist charges. One oxygen atom has a +1 charge, whereas the other has a -1 charge.
By transforming lone pairs to bonds, check the stability of atoms and reduce their charges. Because both O2 atoms have charges, and those charges are considerable, the above structure is unstable.
Furthermore, one oxygen atom does not have eight electrons in its final shell, making the configuration above exceedingly unstable. As a result, we must lower charges by converting lone pairs to bonds, as shown below.
There are no charges on O2 atoms in the last structure, and the valence shell possesses eight electrons to fulfill the octet in both oxygen atoms.
Occurrence of O2
O2 is all around us.
After hydrogen and helium, O2 is the third most plentiful element in the universe. It is the most prevalent element in the Earth’s crust in terms of mass. To make minerals like quartz and sand, oxygen forms compounds with silicon and other atoms.
Oxygen is the atmosphere’s second most abundant gas. It makes up about 21% of the air we breathe. On the other hand, it’s a highly reactive gas that blends very well with other aspects.
Plants and other photosynthetic organisms replenish it. O2 also makes up the majority of the Earth’s oceans in terms of mass.
Isotopes of Oxygen and Their Uses
O-17 and O-18 Isotopes of Oxygen and Their Applications
O-17 and O-18 are made through fractional distillation, electrolysis, or thermal diffusion of O2 gas.
In chemical kinetics and mechanistic investigations, the elemental isotope (mass number = 18) is used as a tracer. However, in NMR spectrum analysis, O-17 (mass number = 17) is used.
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