How can there be oxygen in water?

The oxygen we breathe is a gas and a gas is very different from liquid water. Oxygen, we are told, is one of the ingredients in water and there is commonly plenty of oxygen in the sea for the fishes to breathe. But the oxygen breathed by the see. dwellers is not the same oxygen which is an ingredient of watery To solve these mysteries we need to know a little bit of chemistry.

To a chemist, water is a compound of the elements hydrogen and oxygen. It is made of small particles, each containing one atom of oxygen and two atoms of hydrogen. When you bake a cake, you use eggs, butter, sugar and flour. But the finished cake is very different from its ingredients. A compound, such as water, is also very different from its ingredients.

In their pure form, the elements hydrogen and oxygen are gases, Each atom of oxygen has, eight protons in its central nucleus. Outside the nucleus are eight electrons, two in an inner shall and six in a second shell. An atom has room for eight electrons in its second shell  . which means that the oxygen atom has room for two more electrons.

The hydrogen atom has one proton on in its nucleus and outside it is a single electron. An atom needs two electrons to complete its inner shell and the lone electron of the hydrogen atom is very restless. The oxygen atom, needing two electron’s to complete its second shell, is also very restless. But when one atom of oxygen and two atoms of hydrogen combine, all these problems are solved. The three atoms share their electrons and form a single particle of the compound, water. The compound., like the cake, is very different from its ingredients.

This chemical magic accounts for the disappearance of the oxygen which is an ingredient of water.

But this is not the oxygen which the fishes breathe The gaseous oxygen in the air tends to mix and blend with the water it touches. It dissolves with the water without forming a compound. This free oxygen, unattached to atoms of hydrogen, is the oxygen breathed by the countless sea dwellers. There is free oxygen dissolved in our drinking water, though we cannot see it or smell it. However, maybe we can taste it, for when there is no dissolved oxygen, our drinking water is very flat.

The fishes are happier and healthier where there is a lot of free oxygen in the water. They thrive in running streams and in the wave tossed ocean. Here the oxygen in the air gets a better chance to mix with the water. In calm, stagnant water, there is little or no free oxygen and the fish go somewhere else where they find it easier to breathe.