Sodium's Big Brother

So going back to the fourth period, lets look at some of the more interesting properties of the elements in this row. First we will look at Potassium, a very important element in living systems.


Potassium (K - 19) is an Alkali Metal, the next heavier element in the same group as Sodium and functions in a similar fashion as Sodium in the body. It gets the chemical symbol K from its Latin name Kalium. It oxidizes in air and reacts with water with sufficient heat to ignite the hydrogen gas that is produced, burning with a pink-purple flame. It is found most abundantly as potash, hence the name Potassium (POTASh).  Potash is Potassium Hydroxide (KOH) which is extremely toxic and corrosive. Potassium has one electron in the 4s shell, which it is eager to lose, to have the stable Argon configuration. Thus Potassium generally exists as a positive ion, either in solution or in a salt or mineral form. Pure Potassium is a low density, silvery metal. It can be cut easily with a knife and melts at about 146^oF.

Potassium's most common isotope contains 39 neutrons. Small quantities of ⁴⁰K occur naturally. The ⁴⁰K isotope is radioactive with a half life of over a billion years and is used to date some types of volcanic rocks. It also occurs naturally in foods and is the largest source of radioactivity in the body. It is the seventh most abundant element and is found in Granite and Feldspar.

In the body Potassium is a critical component of nerve function and transmission. It creates an electron action potential across the cell membrane via the Sodium-Potassium Pump. This pump uses ATP to move three sodium ions out of the cell and two potassium ions into the cell, thus creating an electrochemical gradient. This action potential moves along the cell membrane propagating the nerve impulse. Potassium is also important in muscle cells, helping to control the contraction and relaxation of the tissues.

A shortage of potassium in body fluids may cause a potentially fatal condition known as hypokalemia, typically resulting from vomiting, diarrhea or increased urination. Symptoms of Potassium deficiency include muscle weakness, ECG abnormalities, decreased reflex response and in severe cases respiratory paralysis and cardiac arrhythmias.

Sufficient Potassium can generally be consumed by eating a variety of foods. Potassium is present in most fruits, vegetables, meat and fish. Cases of Potassium deficiency are rare in healthy individuals. Foods rich in Potassium include bananas, parsley, dried milk, chocolate, almonds and pistachios, potatoes, avocados, soybeans, and bran.

Certain classes of diuretics (urine increasing drugs) which rid the body of sodium and water have the side effect of also causing potassium loss in urine. Lost Potassium can be replaced by taking a Salt substitute containing KCl. Potassium Chloride has a bitter taste, however, and this form of salt is not very palatable. Tablets and capsules with controlled release KCl are available. High concentrations of KCl can cause tissue damage so it needs to be released slowly to prevent this.

Potassium is also widely used as a fertilizer, since Potassium is essential for plants as well as animals. The next time you are at Home Depot, look on a bag of most commercial fertilizers and there will be a listing such as 10-10-10. This is the NPK rating. It tells you, in relative terms, how much Nitrogen, Phosphorus and Potassium is in that particular brand of fertilizer.

Finally, Potassium as potash (KOH) is a strong base and as such is used in industry to neutralize acids and control pH and is found in industrial cleaners. Potassium Chloride (KCl) is sometimes used in the United States for carrying out the death penalty via lethal injection.