What Are Chemical Bonds?
A chemical bond is a lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably.
Types of Chemical Bonds
1. Ionic Bonds
Ionic bonds form when electrons are transferred from one atom to another, creating positively charged cations and negatively charged anions that attract each other. They typically form between metals and non-metals.
Examples: Sodium chloride (NaCl), Magnesium oxide (MgO), Calcium chloride (CaCl₂)
Properties of ionic compounds:
- High melting and boiling points
- Conduct electricity when dissolved in water
- Hard and brittle crystalline solids
- Soluble in polar solvents like water
2. Covalent Bonds
Covalent bonds form when two atoms share electrons. This sharing allows each atom to achieve a stable electron configuration. Covalent bonds can be single, double, or triple bonds depending on how many electron pairs are shared.
Examples: Water (H₂O), Carbon dioxide (CO₂), Methane (CH₄), Oxygen (O₂)
Properties of covalent compounds:
- Generally lower melting and boiling points than ionic compounds
- Poor conductors of electricity
- Can be soluble or insoluble in water
- Exist as gases, liquids, or soft solids
3. Metallic Bonds
Metallic bonds occur between metal atoms where electrons are shared freely among a lattice of positive ions in a "sea of electrons". This gives metals their characteristic properties.
Properties of metallic compounds:
- Excellent electrical and thermal conductivity
- Malleable and ductile
- Lustrous (shiny) appearance
- High melting points (generally)
Bond Polarity
The polarity of a covalent bond depends on the difference in electronegativity between the two atoms. Bonds can range from nonpolar covalent (equal sharing) to polar covalent (unequal sharing) to ionic (electron transfer).