Chemistry Lecture: Quantum Numbers and Electron Configuration

Defining Ground States:
- Ground state refers to the lowest energy condition.
- Sodium example (number 11): High energy electron in 3s; previous configuration: neon leading to 3s¹.
**Determining Quantum Numbers and Configurations: **
- Ground state electron of sodium reinforces the quantification process with clear modeling systems.

Atomic Size Trends Across and Down Periods:
- Across the period: atomic size decreases as protons increase, pulling electrons closer.
- Down a family: atomic size increases due to increased shielding from inner shell electrons.
Relation to Positive and Negative Ions:
- Neutral vs. charged atomic configurations lead to variations in behavior, such as:
- Positive ions are smaller than neutral atoms (e.g. Magnesium ions).
- Negative ions (gain of electrons) are larger than neutral atoms (e.g. Cl⁻).
Physical Definitions of Metals:
- Chemical definitions involved are based on ionization energy measurements.

Ionization Energy:
- Defined as energy needed to remove an electron.
- As atomic size decreases, ionization energy increases.
- Overview of metal vs. non-metal character: Greater ionization energy connotes less metallic behavior.

Electron Affinity Defined:
- Defined as how well an atom gains electrons (neutral gas atom reacting with an electron).
- General trends show that electron affinity increases across a period and decreases down a group due to increasing atomic size.

Electronegativity Definition:
- How well an atom pulls on shared electrons.
- Small atoms generally have higher electronegativity as they hold electrons closer.
Pauling Scale:
- Identifies trends showing electronegativity increasing left to right and decreasing scan.