Chemical Bonding and Molecular Structure
1.0 Ionic Bond or Electrovalent Bond
1.0 Ionic Bond or Electrovalent Bond
An ion is an atom or group of atoms which has acquired charge due to the loss or gain of one or more electrons. When an atom gains an electron to form a negative ion (anion), it will increase in size. On the other hand, when an atom loses an electron to give positive ion (cation), it will contract. The electron lost or gained is always from the outermost shell.
When two atoms, one of which can lose one or more electrons to attain a noble gas configuration and the other can receive these electrons and thereby acquire a noble gas configuration, they are said to be bonded by an ionic bond. Since the loss and gain of electrons by atoms results in the formation of ions, ionic bond is formed when two ions interact with each other and are thus held together by electrostatic attraction. The formation of potassium chloride ($KCl$), is illustrated below.
From the above illustrations, it is clear that the formation of an ionic compound is obviously related to the ease of formation of the cations and anions from the neutral atoms which depends on two main factors:
$1.$ Ionization energy: Lower the value of ionization energy of an atom, greater will be the ease of formation of the cation from it.
$2.$ Electron affinity: Higher the electron affinity of an atom, greater the ease of formation of the anion from it.
