Chemical Structure of Seawater

In oceanography-the study of the oceans,  the phrase “chemical structure” is used  in reference to the chemical composites or particles that make up and are responsible for peculiar features and certain characteristics associated with seawater. Put in other words, seawater may look slightly blue from some distance, somehow white and foamy when you scoop it in your hands and taste salty on your tongue, but there’s more to its chemical composition or structure  than meet the eye.

Seawater contains dissolved materials and certain elements from the earth’s crust as well as dissolved gases such as oxygen and carbon. But before taking a look at the chemical structure of seawater, it’s worth pointing out that its chemical composition do sometimes vary in relation to the part of the world in which a particular ocean or seawater is located and sometimes, its nearness to other water bodies.

In most cases, however, seawater contains the following dissolved chemical elements in differing quantities:


Sulfur as a naturally occurring chemical element reacts with carbon and reduces oxidants most especially oxygen (which can also be found in seawater). It has a percentage of 0.019 in seawater composition.


With a percentage of 85.84, oxygen is the most prominent composite of seawater. It’s very soluble in water and usually bonds with hydrogen to make water and for that matter seawater what it is; the most abundant substance on our Planet.


Hydrogen is the second highest contributor to the structure of seawater with a percentage of 10.82. It combines with oxygen to make up a sizable structure of water found in our oceans.


It is the chemical element most responsible for the salinity or salty taste typical of seawater. Sodium ion is reactive in water and very soluble in water, hence very abundant and definite in the structure of seawater. It forms a percentage of 1.08.


Chloride has a percentage of 1.94 in the structure of seawater and is very influential in the sense that its ions usually reacts with and counterbalances sodium ions (making up 55% of salt found in seawater); a scenario which is responsible the table salt (sodium chloride) we’re left with when seawater is evaporated.


Calcium is alkaline and one of the least chemical contributors to the structure of seawater with a percentage of 0.04, but among the most naturally occurring and dissolved elements in the earth’s crust and oceans. It’s also found in the bones and body of fish living in the sea.

Other chemical elements that are available and form the structure of seawater are bromine, carbon, magnesium and potassium.