Properties of Compounds: Ionic vs. Covalent

Study Notes

Properties of Compounds: Ionic vs. Covalent

Ionic compounds exist only as crystalline solids under normal atmospheric conditions, while covalent compounds can be solid, liquid, or gas.
Covalent bonding involves sharing electrons, resulting in weaker intermolecular attractions compared to ionic bonding, where full ionic charges and rigid crystal lattice structures dominate.
Sodium chloride (NaCl), an ionic compound, serves as a common flavoring and preserving agent.

Melting and Boiling Points

Ionic compounds have higher melting and boiling points due to the strong electrostatic forces holding the ions in a crystal lattice.
Covalent compounds have lower melting and boiling points because they exhibit weak intermolecular attractions, requiring less thermal energy to separate molecules.

Hardness and Brittleness

Ionic compounds are hard and brittle due to their rigid crystal lattice structure, making them difficult to scratch but prone to shattering.
Covalent compounds are soft and flexible, as their molecules are weakly attracted to one another, allowing displacement.

Polarity of Compounds

Ionic compounds demonstrate high polarity, resulting from a significant electronegativity difference (greater than 1.9) between constituent elements.
Covalent compounds may be polar or nonpolar based on electronegativity differences; polar covalent bonds occur with differences between 0.5 and 1.9, while nonpolar covalent bonds occur with differences less than 0.5.
Diatomic molecules (e.g., N₂, O₂, H₂) consist of identical nonmetallic elements and always result in nonpolar covalent bonds.

Solubility in Water

Ionic compounds are generally soluble in water due to the attraction of polar water molecules to the charged ions.
Covalent compounds are often less soluble in water; "like dissolves like" applies, where substances with similar polarities can dissolve each other.

Flammability

Ionic compounds are typically less flammable since they lack carbon and hydrogen, which are present in many covalent compounds.
Organic covalent compounds can be quite flammable, while some need specific conditions to ignite; for example, water is difficult to ignite despite being a covalent compound.
Liquefied Petroleum Gas (LPG), a covalent compound, is flammable and used as a fuel.

Conductivity

Ionic compounds conduct electricity and heat effectively when dissolved in solution, due to the presence of mobile ions.
Covalent compounds, lacking mobile charged particles, act as electrical and thermal insulators, leading to poor conductivity.

Electronegativity and Bond Polarity

Electronegativity measures an atom's ability to attract electrons in a bond, influencing bond polarity.
Using electronegativity differences allows the prediction of whether a compound will be ionic, polar covalent, or nonpolar covalent.
Nonpolar covalent compounds form between atoms with minimal electronegativity differences.
A significant electronegativity difference between metallic and non-metallic elements generally results in ionic compounds, while smaller differences yield polar covalent bonds.

Description

This quiz explores the fundamental properties of ionic and covalent compounds, including their states under normal conditions, melting and boiling points, and physical characteristics. Understand the differences in bonding, hardness, and brittleness between these two types of compounds.