Ions in Sea Water

The surface of the planet is made up of land and water. Some of the water on land is fresh water, while much of the planet's water is in oceans or seas. If you've ever been knocked over by a big oceanic wave and swallowed a gulp of seawater, you are keenly aware that seawater is salty. It is the saltiness of the water that signifies the presence of ions in seawater.

What is seawater?

Seawater is defined simply as water from the ocean, but it is much more than that. Seawater is often an underappreciated substance. In reality, seawater is a complex mixture of mostly pure water-two hydrogen atoms covalently bonded to one oxygen atom-and other components, chiefly ions. The ions in seawater create a positive or negative charge. These ions mainly come from components in rocks known as salts.

What are salts?

Salts are ionic compounds that, when dissolved in water, release ions. Salt compounds are electrically neutral, but, according to the National Oceanic and Atmospheric Administration, the released ions are electrically charged atomic particles. Both positive particles, or cations, and negative particles, or anions, are released as the salts break down from the erosion of falling rain.

How do salts get in the ocean?

Rain is slightly acidic, due to carbon dioxide from the air, and water acts as a solvent because of its high polarity, or unequal distribution of shared electrons resulting in a negative pole at the oxygen atom and two positive poles at the hydrogen atoms. When rain falls over land it erodes the rock, and the acids and water further break down the rocks, releasing salts and the ions therein. The salts and their ions wash through streams and rivers, eventually dumping into the ocean.

What kind of salt ions are found in the ocean?

There are several types of salts and therefore several types of ions. The most common salt ions found in seawater are chloride and sodium. In fact, 90 percent of all the salt ions found in seawater are chloride and sodium. The rest of the ions are mainly sulfate ions, magnesium ions, calcium ions, bicarbonate and potassium ions. Interestingly enough, seawater can contain a lot more than ions. Every major naturally occurring element has been found in seawater, from gold to lead.

Why doesn't seawater get saltier every time it rains?

Seawater remains in a relatively constant state of salinity. By measuring the amount of chlorine in seawater, scientists have been able to deduce the ratio of the major salts over time. Seawater has remained constant for about a billion years. This is called a state of equilibrium. While there is a constant intake of ions into the sea, there is an equal amount of ion output. The output of ions occurs mainly as sediment, salt deposits left after seawater has evaporated and hydrothermal vents.

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