When a bond is broken, energy is absorbed, and when a bond is formed, energy is released. The higher the electronegativity, the more the atom attracts electrons.
Types of Bonds
Ionic Bonds
Ionic bonds occur when a metal transfers electrons to a non-metal. The element with a higher electronegativity becomes the negative ion, while the element with less electronegativity becomes the positive ion. For example, Na+ and Cl-. If the difference in electronegativity is more than 1.7, then the bond is ionic.
Properties of Ionic Substances (Ionic Bonds)
- Hard
- Good conductors of electricity as a liquid but poor conductors of electricity as solids
- High melting and boiling points
- Dissolves in polar substances, like water
Covalent Bonds
Covalent bonds occur when two non-metals share electrons. If the electronegativity is less than 1.7, it is a covalent bond.
Types of Covalent Bonds
- Non-polar Covalent Bonds: No electronegativity difference, such as diatomic elements (BRINCIHOF)
- Polar Covalent Bonds: There is a difference in electronegativity. The greater the electronegativity difference, the more polar the bond is.
Molecular Substances (Covalent Bonds)
- Soft
- Poor conductors of electricity
- Low melting and boiling points
- Does not dissolve in water or polar substances
Network Solids (Covalent Bonds)
- Hard
- Poor conductors of heat and electricity
- High melting points
- Insoluble in water
- Bonded in a continuous structure of covalent bonds, very strong
Metallic Bonding
Metallic bonding occurs in metals and contains mobile electrons. It is hard, conducts heat and electricity in the solid or liquid state, and has high melting and boiling points.
Unit Molecules
Polar Molecule
A polar molecule must contain polar bonds and be asymmetrical in shape. Examples include HC, H2O, and NH3.
Non-polar Molecule
A non-polar molecule is symmetrical in shape, such as diatomic elements (BRINCIHOF).
VSEPR Theory
The VSEPR theory states that unshared pairs of electrons (lone pairs) on the central atom repel the most and predicts the shape of the bonded molecule. Electrons around the central atom arrange themselves as far apart from each other as possible.
Coordinate Covalent Bonds
Coordinate covalent bonds occur when one atom contributes both electrons to the shared pair.
Intramolecular and Intermolecular Forces
Intramolecular forces hold the atoms together, while intermolecular forces hold the molecules together.
Four Types of Intermolecular Forces (IMF)
- Dipole-Dipole
- Molecule-ion Attraction
- Hydrogen Bond
- Van der Waal's forces
Types of Solids
There are more than four types of solids, including:
- Ionic Solids: Composed of positive and negative ions that are ionically bonded to each other. They have high melting and boiling points, are usually hard, and soluble in water. Ionic compounds conduct electricity in the liquid phase but not in the solid phase.
- Molecular Solids: Covalently bonded nonmetals, diatomic elements, and compounds. They are soft, have low melting and boiling points, and are poor conductors of heat and electricity.
- Metallic Solids: Formed by metallic elements and have metallic bonding. They are hard, conduct heat and electricity, and have high melting and boiling points.
- Network Solids: Bonded in a continuous structure of covalent bonds, making them very strong and poor conductors of heat and electricity.
Understanding the difference between electronegativity and bonding between atoms is crucial in chemistry and has implications in various fields, from finance to biology. Electronegativity values and the types of bonds are important concepts to grasp when studying the properties of different compounds and their behavior under various conditions.
