Lecture Notes: Ionic vs. Covalent Bonds

Basic Structure of an Atom

Atoms consist of three main parts:
- Protons: Positively charged particles.
- Electrons: Negatively charged particles, usually equal in number to protons to maintain neutrality.
- Neutrons: Neutral particles, contribute to the atomic mass.
Periodic Table Example:
- Beryllium (Be) has 4 protons and likely 4 electrons, atomic mass is a sum of protons and neutrons (9 for Be, 4 protons + 5 neutrons).

Electron Levels:
- 1st level: can hold 2 electrons (full/stable when filled).
- 2nd level: can hold 8 electrons (full/stable when filled).
- Atoms bond to fill these electron levels and become stable.

Definition: Atoms share electrons to fill their outer electron levels and become stable.
Example: Oxygen molecule (O₂)
- Each oxygen atom has 8 protons, 8 neutrons, and 8 electrons.
- Electrons are distributed as: 2 in the first level (stable), 6 in the second level (unstable).
- Two oxygen atoms share electrons to fill the outer level, becoming stable.

Definition: One atom donates an electron to another, resulting in one positive and one negative ion which attract each other.
Example: Sodium Chloride (NaCl)
- Sodium (Na): 11 protons, 11 electrons (1 in the outermost level, unstable).
- Chlorine (Cl): 17 protons, 17 electrons (7 in the outermost level, unstable).
- Sodium donates one electron to chlorine, resulting in:
  - Sodium becomes positively charged (more protons than electrons).
  - Chlorine becomes negatively charged (more electrons than protons).
- This opposite charge attraction forms the ionic bond.

Covalent Bonds: Sharing of electrons, typical in molecules like O₂.
Ionic Bonds: Transfer of electrons, results in charged ions, typical in compounds like NaCl.

Both bond types aim to achieve stable electron configurations for the participating atoms.
Covalent bonds involve sharing, while ionic bonds involve transfer and charge attraction.