Introduction to Ionic Bonding and Ionic Compound Properties

Ionic Bonding

Concept of Ionic Bonding

Ionic bonding refers to the attractive force that holds ions together in a chemical compound. This type of bond typically forms when electrons are transferred from one atom to another, resulting in the formation of oppositely charged ions.

• Ionic bonds occur between metals (which lose electrons to become cations) and nonmetals (which gain electrons to become anions).

• Metals tend to lose electrons and form positive ions (cations).

• Nonmetals tend to gain electrons and form negative ions (anions).

Example: Sodium (Na) transfers an electron to chlorine (Cl) to form sodium chloride (NaCl):

$\text{Na} \rightarrow \text{Na}^+ + e^-$ $\text{Cl} + e^- \rightarrow \text{Cl}^-$ $\text{Na}^+ + \text{Cl}^- \rightarrow \text{NaCl}$

• Covalent compounds (where atoms share electrons) will be discussed later.

Example Question

Which of the following species has bonds with the most ionic character?

• a) SO2

• b) AlCl3 (Answer: AlCl3)

• c) H2O

• d) Cl2

Explanation: AlCl3 has the greatest difference in electronegativity between the metal and nonmetal, resulting in the most ionic character.

Ionic Compound Properties

Physical and Chemical Properties of Ionic Compounds

The properties of ionic compounds are determined by the strong electrostatic forces between the oppositely charged ions in their crystal lattice structure.

Physical State	Electrical Conductivity	Melting/Boiling Points	Brittleness
Solid at room temperature	Good conductor when dissolved in water (aqueous solution)	High melting and boiling points	Brittle (breaks easily due to repulsion of like charges when structure is disturbed)

• Solubility: Many ionic compounds are soluble in water.

• Conductivity: Ionic compounds conduct electricity when molten or dissolved, but not in solid state.

Example Question

Which of the following compounds has properties most similar to sodium chloride (NaCl)?

• a) Carbon dioxide, CO2

• b) Ammonia, NH3

• c) Potassium bromide, KBr (Answer: Potassium bromide, KBr)

• d) Chlorine gas, Cl2

Explanation: KBr is also an ionic compound, so it shares similar properties with NaCl.