An ion is an atom or group of atoms that has a net positive or negative charge. The name ion comes from the Greek word ion which means "that goes", because the charged particles go towards a charged electrode or away from it.
Ionization is the formation of electrically charged molecules or atoms. Atoms are electrically neutral since negatively charged electrons are equal in number to positively charged protons in nuclei. The number of protons in an atom remains the same during common chemical changes (called chemical reactions), but electrons can be lost or gained.
The loss of one or more electrons from a neutral atom forms a cation , an ion with a net positive charge. For example, a sodium (Na) atom can easily lose an electron to form the sodium cation, which is represented as Na +.
On the other hand, an anion is an ion whose net charge is negative due to an increase in the number of electrons. For example, a chlorine atom (Cl) can gain an electron to form the chloride ion Cl-
As sodium combines with chlorine to form sodium chloride (common table salt), each sodium atom gives up one electron to one chlorine atom. In a sodium chloride crystal, the strong electrostatic attraction between oppositely charged ions holds the ions firmly in place, establishing an ionic bond. It is then said that sodium chloride is an ionic compound because it is made up of cations and anions.
An atom can lose or gain more than one electron, such as the ferric ion with three positive charges (Fe + 3) and the sulfide ion with two negative charges (S =). These ions, like the sodium and chloride ions, are called monatomic ions because they contain only one atom. With some exceptions, metals tend to form cations and non-metals, anions.
Furthermore, it is possible to combine two or more atoms and form an ion that has a net positive or negative charge. Ions that contain more than one atom, such as OH- (hydroxide ion), CN- (cyanide ion), and NH4 + (ammonium ion) are called polyatomic ions.
The minimum energy required to separate an electron from an isolated atom (or ion) in its ground state is known as ionization energy , and it is represented in kJ / mol. The magnitude of this energy is a measure of how "tightly" the electron is bound to the atom. The higher the ionization energy, the more difficult it is to remove the electron from the atom.
