What Is a Strong Electrolyte?

Addressed in chemistry, a strong electrolyte is a substance that dissolves completely when placed into water. When it dissolves, a strong electrolyte dissociates into both positively and negatively charged molecules or atoms, called cations and anions respectively. These electrolytes are capable of conducting electricity in their dissolved states but not in their solid forms. They are usually salts and strong acids and bases.

Electrolytes have three categories: strong, weak, and nonelectrolytes. A strong electrolyte dissociates completely or nearly completely when put in water, whereas a weak electrolyte only dissociates partly and a nonelectrolyte remains whole. Most molecules which can be broken apart in water are held together by ionic bonds.

Ionic bonds occur when two atoms or molecules share one electron. When the bond breaks, one of the atoms retains the shared electron. Since electrons are negatively charged, the atom that gained an electron becomes negatively charged, and the atom which lost the electron becomes positively charged. The positive charge results when number of protons, which are positively charged, in the atom's nucleus no longer equal the number of electrons, which are negatively charged.

The formation of these positively and negatively charged ions, called cations and anions, is what allows a strong electrolyte to conduct electricity. The more ions in the solution, the stronger the electrical conduction. Electrolytic cells use this principle. A strong electrolyte is dissolved in water and two rods, called the cathode and anode, are connected to positive and negative electrical output. The electric current travels through the anode, across the solution and exits from the cathode, creating an electrical circuit.

Since strong electrolytes are either strong acids, salts, or strong bases, they can often be determined by looking at their molecular formula. Salts are generally a metal bonded to another element. Sodium chloride (NaCl), commonly known as table salt, is one of the most easily recognized salts. The molecular formula for strong bases also usually begins with a metal but generally ends with a hydroxide molecule (OH). If nitrogen (N) is in the molecular formula for a base, it is most likely a weak, rather than strong, base and therefore also a weak electrolyte.

Most acids are weak acids and can easily be identified by the hydrogen atom (H) starting their molecular formulas. The seven strong acids, however, also begin with hydrogen and are simply memorized by scientists who work with strong electrolytes. The strong acids are hydrogen bromide (HBr), hydrogen iodide (HI), sulfuric acid (H₂SO₄), nitric acid (HNO₃), perchloric acid (HClO₄), chloric acid (HClO₃), and hydrochloric acid (HCl).