Lecture Notes: Chemical Bonds and Relationships

Key Idea: Bonds in Chemistry and Life

Analogy with Human Relationships:
- Relationships in life are compared to chemical bonds: they require different things based on the type.
- Importance of balance and distance in relationships, similar to atoms.

Why Atoms Bond:
- Atoms aim to reduce their overall energy by balancing attractive and repulsive forces.
- Electrostatic force: attraction between electrons of one atom and protons of another.
- Atoms bond to achieve a state of minimum energy.
Bond Length:
- Perfect distance between two nuclei where attractive and repulsive forces cancel out.
- Example: Chlorine gas (Cl2) has a bond length of 0.00199 nm with energy of -239 kJ/mol.

Covalent Bonds:
- Form when atoms share electrons.
- Non-polar Covalent Bonds: Electrons are equally shared between identical atoms.
- Polar Covalent Bonds: Electrons are unevenly shared, causing a separation of charges (polarity).
- Example: H2O is a polar covalent bond due to differing electronegativities (hydrogen: 2.1, oxygen: 3.5).
Electronegativity:
- Measure of how strongly an atom holds shared electrons.
- Differences in electronegativity influence bond polarity.
Ionic Bonds:
- Formed by the transfer of electrons from one atom to another, creating positive and negative ions.
- Strong polar bonds due to the complete separation of charges.
- Example: NaCl (table salt) forms ionic bonds.
- Energy calculation using Coulomb's Law.

Ionic Compounds:
- Often crystalline solids.
- Soluble in water; conduct electricity when dissolved.
Covalent Compounds:
- Can be softer solids, liquids, or gases.
- Often not soluble in water; solutions don't conduct electricity.