![]() ![]() Then, in 1771, the radical, free-thinking, British theologian-scientist Joseph Priestley, intrigued by how a burning candle placed in an airtight jar was extinguished after sometime and how a mouse died within a few minutes of being placed inside one, began conducting a series of experiments to understand why this happened. The Italian painter-scientist Leonardo da Vinci (1452-1519) is believed to be the first to suggest that air consists of at least two different gases, one of which was consumed during burning. The process of burning, and the reactions involved, were also not clearly understood then, mainly because of the lack of proper laboratory equipment in those days for collecting air samples and examining them. It may seem somewhat naïve now, but air was formerly considered to be a single element. Before that, for more than two millennia, it was believed that air was one of the five basic elements, the other four being earth, water, fire, and ether. The composition of air was somewhat of a mystery till around 250 years ago. Meaning, as long as we ensure we have enough trees and plants, we can ensure the replenishment of atmospheric oxygen. Thus, the oxygen we breathe is mainly a by-product of photosynthesis. All of these life forms use sunlight to convert inorganic compounds like carbon dioxide and water into carbohydrate molecules inside which they store chemical energy, and oxygen molecules which they release into the air. Half of the available oxygen is produced by photosynthetic organisms in water, the other half by plants and trees on land. The fact is, the process of photosynthesis is responsible for almost all the free, breathable oxygen gas in our atmosphere. But, what’s even more amazing is that most of us take this availability for granted and fail to realise or remember how this is made possible. It is so highly reactive, it’s amazing that we have free oxygen available in the atmosphere for breathing. It also constitutes two thirds of the mass of the human body.Ī chemically reactive, non-metallic element, oxygen forms compounds with almost all chemical elements except the noble gases. Besides, oxygen dissolved in oceans and other water bodies enables fish and marine life to breathe. Oxygen is the most abundant element on the earth, accounting for around 21% of the volume of its atmosphere, around 50% of the mass of its crust, and nine tenths of the mass of water. Moreover, it’s the presence of oxygen in our atmosphere that sets our planet apart from all the others in our solar system. Humans and almost all life forms on earth need it for every breath they take and for producing energy through the combustion of food within their body. The first element of Group 16 of the periodic table, oxygen is the element on which our very existence on earth depends. ![]()
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