How long can you hold your breath? Well, for me it's not any more than 10 seconds! So what is it that we inhale through our nostrils every other second? It is a gas! But which gas is it, that is making us thrive on this beautiful planet of ours? Well! It's the omnipresent Oxygen!
Oxygen is one of the most significant components present in the atmosphere. In its gaseous diatomic form, this element is essential for the survival of living organisms on the planet. Oxygen has an atomic number of 8 and belongs to group 16, period 2 of the modern periodic table. It is the first member of the chalcogen family. 21% of the earth’s atmosphere is occupied by oxygen, and more than half of the earth’s crust contains metals in their oxide forms.
Combustion of fuels in spacecraft and rocket launching also requires oxygen. Following hydrogen and helium, oxygen is the third most abundant element. Oxygen has large-scale applications right from industries to cellular respiration in biological systems. Plants play an important role in maintaining oxygen saturation in the atmosphere; it also helps in decreasing the carbon dioxide content in the air.
TABLE OF CONTENTS
Dioxygen or popularly called as oxygen, is one of the most abundant allotropes of elemental oxygen and is represented by the chemical formula O2. It is also sometimes referred to as oxygen gas, molecular gas or dioxygen.
One of the most prevalent allotropes of elemental oxygen, dioxygen, sometimes known as oxygen, is denoted by the chemical formula O2. It can also be referred to as dioxygen, oxygen gas, or molecular gas.
The Lewis structure of oxygen is represented by two double bonds between two oxygen atoms. Hence O2 molecule is linear, and it has strong electronegativity and reactivity due to lone pairs of electrons present on both the oxygen atoms. The molecule of oxygen can be represented as O=O, and the bond between the two atoms is covalent. The bond length of O2 molecule is 121 pm, whereas it's its bond energy is 498 kJ mol-1.
The most common allotrope of elemental oxygen is dioxygen (O2).
The next major allotrope is Trioxygen (O3) commonly known as ozone which is a very reactive allotrope of oxygen. Ozone is produced in the upper atmosphere when O2 combines with atomic oxygen made by the splitting of O2 by ultraviolet (UV) radiation.
There are primarily two methods of producing oxygen gas industrially.
Examples: Na2O, CaO, BaO, CuO are basic oxides and are acidic oxides.
In this molecule, oxygen changes its oxidation state from 0 in O2 to +2 in MgO so it undergoes reduction while oxidising Mg.
[Hydrated Iron Oxide]
In the periodic table, oxygen belongs to Group 16. But owing to certain characteristic features of oxygen, it shows some exceptional properties unlike the other members of its family. In fact, the main reasons for the anomalous properties of oxygen are small atomic radii, high electronegativity and absence of vacant d-orbitals. The anomalous properties of oxygen are as follows:
Q.1. Why does dioxygen exist as gas whereas sulphur exists as solid?
Answer: The O—O bond is comparatively weaker than the S—S bond owing to greater inter-electronic repulsions in the smaller sized smaller-sized oxygen atoms.
Also, due to smaller atomic radii and greater electronegativity of oxygen, it forms multiple bonds. As a result, molecular oxygen exists as O2 molecules held together by weak van der Waals forces. Hence, at room temperature, it exists as a gas.
Sulphur on the other hand has a lower tendency to form multiple bonds due to larger radii. Due to a larger atomic size, and low electronegativity, sulphur forms strong S—S single bonds, which explains its catenation property and so it exists as S8 molecules with a puckered-ring structure. As a result, sulphur is a solid due to a larger association, at room temperature.
Q.2. Does oxygen react with other elements of its own group?
Answer: Yes, it readily attracts electrons owing to high electronegativity and forms oxides with other elements of its group.
Q.3. Which of the following does not give oxygen on being heated?
Solution: All the given salts except ammonium dichromate liberate oxygen on heating. When ammonium dichromate is heated it decomposes to give off nitrogen gas and chromium oxide.
Q.4 Which of the following is not an acidic oxide?
Solution: Metallic oxides are basic and non-metallic oxides are generally acidic. Hence, iron oxide is the only option which is a metallic oxide and it is basic in nature.
Q.5 Find out in which of the following compounds oxidation state of oxygen would be zero? Which of the following compounds would have a zero oxidation state of oxygen?
Solution: Due to the highest electronegativity of fluorine, it always exists in -1 state and hydrogen exists as +1. Hence in hypofluorous acid (HOF) oxidation state of oxygen is zero. Only with fluorine, oxygen exhibits +1 and 0 oxidation states. Only with fluorine, does oxygen exhibit a +1 oxidation state.
Q.1. Does Oxygen react with alkali metals?
Answer: Oxygen has a high reactivity for electropositive elements and especially with alkali metals (Group I elements). It is recommended that alkali metals should be kept away from oxygen to avoid an explosion due to oxidation. Metals at the bottom of the group are more reactive than those at the top.
Q.2. Can oxygen exist as solid, liquid or gas?
Answer: At suitable temperature conditions oxygen can be obtained in all three states of matter. For example, solid oxygen can be obtained at normal atmospheric pressure at a temperature below 54.36 K (−218.79 °C). At room temperature oxygen exists as a gas. Solid and liquid oxygen is bluish in colour.
Q.3. Is oxygen available on mars?
Answer: According to the scientists of NASA, mars does have oxygen, but it is not sufficient enough to just roam around and breathe in fresh oxygen as we do on Earth. This is because the density of oxygen on Mars is times that of oxygen on Earth.
Q.4. Can oxygen ever become extinct from earth?
Answer: Few studies state that one billion years from now, the earth will have a very minimal amount of oxygen making it difficult for all aerobic processes to occur. But yet there is hope to reverse the process, only if we start following a sustainable process of livelihood.