Oxygen is a chemical element — a substance that includes only one sort of atom. Its atomic number is 8, and its official chemical symbol is O. An oxygen atom has eight protons in its nucleus. At normal temperature, oxygen is a colourless, odourless, and tasteless gas. Oxygen exists as a molecule in nature. Dioxygen, or O₂, is formed when two oxygen atoms establish a strong covalent double bond. 

Occurrence In Nature

1. After hydrogen and helium, it is the third most plentiful element in the universe. 
2. 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. 
3. It is the atmosphere’s second most abundant gas. Oxygen makes up about 21% of the air we breathe. Oxygen, on the other hand, is a highly reactive gas. It blends very well with other aspects. Plants and other photosynthetic organisms replenish it. 
4. Oxygen also makes up the majority of the Earth’s oceans in terms of mass. Two hydrogen atoms and one oxygen atom make up a water molecule (H₂O). Despite the fact that water has more hydrogen atoms, it has less mass. Nearly 90% of water’s bulk is made up of oxygen. 
5. Because our bodies are 70% water, it is the most abundant element in the human body (by mass). 

Properties of Oxygen 

Physical Properties of Oxygen 

1. The gas oxygen is colourless, odourless, and tasteless. 
2. At a temperature of -182.96°C (-297.33°F), it transforms from a gas to a liquid. 
3. The resulting liquid is slightly bluish in colour. 
4. At a temperature of -218.4°C (-361.2°F), liquid oxygen can be solidified or frozen. 
5. Oxygen has a density of 1.429 gms per litre. 
6. Air, by comparison, has a density of 1.29 grams per litre. 
7. There are three allotropic types of oxygen. Allotropes are distinct physical and chemical forms of the same element. 
8. Normal oxygen, also known as diatomic oxygen or dioxygen, nascent, atomic, or monatomic oxygen, and ozone, often known as triatomic oxygen, are the three allotropes of oxygen. The three allotropes are distinct in a variety of ways. 

Chemical Properties of Oxygen 

1. The most essential chemical feature of oxygen is that it aids in burning. That is, it aids the burning of other objects. One example is the combustion (burning) of charcoal. 
2. At ambient temperature, oxygen also reacts with elements, making charcoal almost pure carbon (C). 
3. One example is rusting. Rusting is a chemical reaction that occurs when a metal reacts with oxygen. When iron rusts, it reacts with oxygen, which reacts with a wide range of chemicals. 
4. One example is decay. Once-living matter reacts with oxygen in the process of decay. Carbon dioxide (CO₂) and water are the major byproducts of decomposition (H₂O). 

Preparation of Oxygen 

Oxygen can be created in a variety of methods in the laboratory 

Laboratory Preparation of Oxygen 

1. In the presence of finely divided metals and manganese dioxide, hydrogen peroxide decomposes to produce water and dioxygen. 

2H₂O₂ (aq) → 2H₂O (l) + O₂ (g) 

1. O₂ is formed when the oxides of a few metals disintegrate in the presence of heat. 

2HgO (s) → 2Hg (l) + O₂ (g) 

2PbO₂ (s) → 2PbO (s) + O₂ (g) 

1. Heating causes chlorates, permanganates, and nitrate salts to break down, releasing oxygen. 

2KClO₃ → 2KCl + 3O₂ 

Industrial Preparation of Oxygen 

Air is used to produce O₂ on a huge scale. Carbon dioxide and water are removed from the air, and the remaining gases are extracted through fractional distillation and liquefaction, releasing nitrogen and oxygen. 

Blood Oxygen Levels 

The oxygen levels in the blood that passes through the arteries of the body are known as blood oxygen levels (arterial oxygen).

The oxygen and carbon dioxide levels in blood collected from an artery can be evaluated before they enter body tissues in an ABG test. An ABG machine (blood gas analyzer) will be used to determine your blood oxygen levels in the form of partial pressure of oxygen (PaO₂). 

Normal Oxygen Levels 

An equipment called a pulse oximeter can also be used to test blood oxygen levels.

1. A pulse oximeter’s typical oxygen levels are normally between 95 and 100 percent. 
2. Low blood oxygen levels are defined as those that go below 90% (hypoxemia). 

Blood Oxygen Levels Checked Using the ABG Test 

1. By extracting blood from an artery in the wrist, elbow, or groyne, you can examine your blood oxygen levels. 
2. When the needle enters the artery, you may experience a sharp pain. 
3. An ABG machine (blood gas analyzer) will be used to determine your blood oxygen levels in the form of partial pressure of oxygen (PaO₂). 

Blood Oxygen Levels Checked Using The Pulse Oximeter 

A pulse oximeter is a compact, portable medical equipment that can be used anywhere.

1. It’s most typically utilised when doctors need to swiftly determine your blood oxygen levels. 
2. It can also be used to track how your body reacts to specific drugs or extra oxygen. 
3. SpO₂, or percent saturation of oxygen in the blood, is a measure of blood oxygen levels. 

Oxygen Concentrators 

An oxygen concentrator is a device that selectively removes nitrogen from a gas supply (usually ambient air) to produce an oxygen-enriched product gas stream. They’re used in industry and as oxygen therapy equipment in hospitals.