Oxygen

Oxygen is one of the most important elements in the periodic table with the chemical symbol O. One of the compounds of Oxygen (O₂) is the main factor for sustaining life on Earth. It is colourless, odourless, and tasteless gas. 

1.0Key Points to Remember about Oxygen

Structure of Oxygen

The oxygen atom contains 8 neutrons and 8 protons in its nucleus, as well as 8 electrons, which revolve around the nucleus in 2 energy shells (K, L). 

• The K shell contains 2 electrons,
• And the L shell has 6 electrons. 

Oxygen, with a valency of 2, can form two bonds with other atoms or need two electrons to complete its shell (shells of electrons contain 8 electrons in the L shell and 2 in K).

The Electronic Configuration of Oxygen is 1s²2s²2p⁴. 

Allotropes of Oxygen 

Allotropes are different forms of the same chemical element, in the same physical state, but having different molecular structures and properties. The atoms of the element vary in their bonding arrangements, which gives differences in the physical and chemical characteristics of the substance. In the context of oxygen, it has three allotropes namely:

1. Dioxygen(O₂): It is the most common allotropes of oxygen present in the environment which is a crucial compound for sustaining life on Earth as animals and plants use O₂ to produce energy.
2. Ozone (O₃): it is most commonly found in the stratosphere (second layer of Earth's atmosphere), and it helps us stay protected from the harmful rays of the sun.
3. Tetraoxygen (O₄): it is a rarer form of oxygen present in the environment that can be manufactured by applying extreme pressure on oxygen molecules. It is of solid form with a deep red color.

Presence of Oxygen 

1. Percent of Oxygen in Air: Oxygen is the second most abundant element in the atmosphere of Earth, followed only by Nitrogen. It occupies about 21% of Earth’s atmosphere by volume. 
2. Earth’s Crust: Oxygen is the most abundant element in the Earth’s crust, constituting about 46% by weight. It is found in water (H₂O) as mixed oxygen, Carbon dioxide (CO₂), and minerals like quartz (SiO₂). 
3. Biological Systems: Oxygen is an asset for sustaining life on Earth. Animals respire for energy production, which helps them work, and plants do photosynthesis to make their food. 

Key Takeaways

• Symbol: O
• Atomic Number: 8
• Atomic Mass: 16 g/mol
• Molecular Formula: O₂ (dioxygen)
• State at Room Temperature: Gas
• Color, Odor, and Taste: Oxygen is colorless, odorless, and tasteless.
• Density: Oxygen is denser than air (1.429 g/L at 0°C and 1 atm).
• Boiling Point: −183°C (90 K)
• Melting Point: −218.79°C (54.36 K)
• Solubility: Slightly soluble in water 

2.0Properties of Oxygen

There are many physical and chemical Characteristics of Oxygen, such as: 

• Physical Properties: As mentioned earlier, Oxygen is a Colorless, odourless, and tasteless gas that supports combustion but does not burn itself. 
• Reactivity: Oxygen reacts with almost every element present on Earth, including Metals, Non-metals, metalloids, and even Organic compounds. This is the reason it is an abundant element in our environment. 
• Electronegativity: Oxygen is a highly electronegative element, which justifies its ability to oxidise other elements with so much power. Electronegativity is a property that indicates how strongly an element can pull shared electrons in a bond. 
• Combustion: Combustion is a chemical reaction in which a substance reacts with oxygen, releasing energy in the form of heat and light. It usually involves the burning of fuels such as wood, coal, or gasoline, where oxygen plays a significant role in the reaction. For Example: 

$C+O_2\to C{O}_2$

• Reaction with Metals: Oxygen, when it reacts with metal, produces oxides of metal that are generally basic in nature. For example: 

$2Mg+O_2\to 2MgO$

• Reaction with Non-Metals: Oxygen reacts with non-metals to form oxides that are acidic in nature. For Example: 

$S+O_2\to S{O}_2$

• Formation of Ozone (O₃): In the stratosphere (second layer of Earth’s atmosphere), Ozone is formed by the reaction of UV rays from the sun. The UV rays break down the oxygen molecule (O₂) into nascent oxygen (O). This nascent oxygen, when it reacts with other oxygen molecules, forms Ozone (O₃). The reaction of this are: 

$O_2\to 2O$

$O_2+O\to O_3$

3.0Forms of Oxygen

Oxygen is present in many forms in the environment, such as: 

• Gaseous Oxygen: Oxygen in its most common form is a colourless, odourless gas (O₂), which is vital for the respiration of animals and combustion processes.
• Liquid Oxygen: Oxygen can be liquefied at extremely low temperatures. −183°C It is applied industrially, particularly in rocket propulsion, welding, and oxygen supply for medical applications.
• Nascent Oxygen: Nascent oxygen refers to oxygen in an active, highly reactive atomic form (O) that is often formed during chemical reactions, such as during the formation of ozone and decomposition of hydrogen peroxide:

$2H_2{O}_2\stackrel{catalyst}{\to }2H_{2}O+O$

• Oxygen Ion: Ion means an element that gains or loses electrons. The Oxygen ion (O^-2) is formed when oxygen gains 2 electrons to satisfy its valence shell (The last shell of an atom). For example, Calcium oxide, Potassium Oxide, etc. 

4.0Uses Of Oxygen

• In Medicine: It is applied for oxygen therapy for patients who suffer from respiratory conditions, anaesthetic procedures, and in the intensive care unit.
• In Industry:
• • Steel Manufacturing: Applied in the blast furnace in smelting iron ore.
  • Welding and Cutting: Oxygen is applied in oxy-acetylene welding at very high temperatures.
  • Rocket Propulsion: LOX or liquid oxygen is used as a propellant in space.
  • In Space Exploration: Supplies oxygen to astronauts aboard the spacecraft.
• In Respiration: Oxygen is used in the respiration process in animals and humans and helps to release energy from glucose($C_6{H}_{12}{O}_6$).

$C_6{H}_{12}{O}_6+6O_2\to 6C{O}_2+6H_{2}O+Energy$