Lecture Notes: Bonding of Atoms

Introduction to Atomic Bonding

Atoms can exist alone or bond with other atoms.
The main goal of atoms is to achieve the most stable or lowest energy state.
Stability is often achieved when the valence shell of an atom is filled with electrons.

Pure unbonded elements are electrically neutral.
Stability often requires a full valence shell.
Octet Rule: Most atoms require eight electrons to fill their valence shell.
- Exceptions:
  - Hydrogen and Helium (require only two electrons).

Definition: Transfer of electrons from a metal to a non-metal.
- Creates oppositely charged ions (cations and anions).
- Example: Sodium chloride (NaCl).
Process:
- Metal loses valence electrons to non-metal.
- Example: Sodium (cation) loses one electron to Chlorine (anion).
- Forms a strong electrostatic attraction.
Structures:
- Ionic compounds form crystal lattices rather than individual molecules.
- Example: Large crystal structures like those in Mexico’s Cave of Crystals.

Definition: Sharing of electrons between atoms.
- Occurs between non-metals.
- Forms molecules.
Nonpolar Covalent Bond:
- Equal sharing of electrons.
- Example: H2 molecule (equal electronegativity).
Polar Covalent Bond:
- Unequal sharing of electrons.
- Example: HCl molecule (chlorine has higher electronegativity).
Bond Capacity:
- Different atoms can form different numbers of covalent bonds.
- Example:
  - Hydrogen forms one bond.
  - Oxygen forms two.
  - Nitrogen forms three.
  - Carbon forms four.