Ions and Ionic Bonds

Introduction

Atoms can gain or lose electrons to achieve a stable electron configuration. When atoms gain electrons, they become negatively charged ions called anions. When atoms lose electrons, they become positively charged ions called cations. The electrostatic attraction between oppositely charged ions forms ionic bonds, creating ionic compounds.

Formation of Positive Ions (Cations)

Metals tend to lose electrons to form positive ions. The number of electrons lost depends on the metal's electronic configuration. The charge of the cation is equal to the number of electrons lost.

Here are some examples:

• Sodium (Na) loses one electron to form Na⁺.
• Magnesium (Mg) loses two electrons to form Mg²⁺.
• Aluminium (Al) loses three electrons to form Al³⁺.

Formation of Negative Ions (Anions)

Non-metals tend to gain electrons to form negative ions. The number of electrons gained corresponds to the charge of the anion. Anions are formed when atoms gain electrons to achieve a stable electron configuration.

Here are some examples:

• Chlorine (Cl) gains one electron to form Cl^-.
• Oxygen (O) gains two electrons to form O^2-.
• Nitrogen (N) gains three electrons to form N^3-.

Summary Table

Atom	Electrons Lost/Gained	Ion Formed	Charge
Sodium (Na)	1	Na+	+1
Magnesium (Mg)	2	Mg2+	+2
Aluminium (Al)	3	Al3+	+3
Chlorine (Cl)	1	Cl-	-1
Oxygen (O)	2	O2-	-2
Nitrogen (N)	3	N3-	-3

Key Terms

• Cation: A positive ion formed when an atom loses electrons.
• Anion: A negative ion formed when an atom gains electrons.
• Ionic Bond: A chemical bond formed through the electrostatic attraction between oppositely charged ions.