Cation
Definition and meaning of Cation in chemistry.
A cation is an ion that carries a positive electric charge. It forms when a neutral atom or molecule loses one or more electrons. Since it has more protons than electrons, the overall charge becomes positive.
In more detail
Metals typically form cations because their outer electrons are loosely held. Removing these outer electrons takes a small amount of energy. When an atom loses electrons, the resulting cation shrinks in size.
This shrinking happens because the remaining electrons repel each other less. The central nucleus then pulls these fewer electrons much closer. Often, the atom loses its entire outer shell of electrons.
Cations are vital to both chemistry and daily life. They link with negative ions called anions to build ionic compounds. These solid compounds include common materials like table salt and chalk.
Cations also dissolve easily in water to carry electrical currents. Inside the human body, dissolved cations do essential work. Sodium and potassium cations move across cell membranes to fire nerves.
Calcium cations allow your muscles to contract and build solid bone. A common mistake is confusing cations with negative anions. You can remember that cats have paws, making cations positive.
Students also sometimes think losing a particle makes the charge negative. However, losing negative electrons always leaves a net positive charge behind. During chemical tests, cations move toward the negative terminal. This negative terminal is called the cathode, which gives cations their name.
Key facts
| Charge | Positive (net) |
|---|---|
| Formed by | Loss of electrons from a neutral atom |
| Size | Smaller than the parent atom |
| Moves toward | Cathode (negative electrode) |
| Common examples | Na+, K+, Ca2+ |
| Field | General Chemistry |
Consider a neutral atom of sodium metal with eleven electrons. It easily gives up its single outer electron to become stable. This loss creates the sodium cation, written as Na+. The sodium cation now has eleven protons but only ten electrons. It then strongly attracts a negative chloride ion, written as Cl-. Together they lock into a crystal lattice to form table salt.
Frequently asked questions
Why is it called a cation?
The name comes from the word cathode. During electrical tests, positive ions move toward the negative cathode.
Is a cation bigger or smaller than a neutral atom?
It is smaller than the neutral atom. Losing an electron reduces crowding, letting the nucleus pull the remaining electrons closer.
Can nonmetals form cations?
Yes, but it is less common than with metals. Nonmetals usually gain electrons to form negative anions instead. However, some nonmetals join together to form positive groups like the ammonium cation.