Atomic Structure and Periodic Trends Essentials

Atomic Structure and Quantum Concepts

Notation: Z (Atomic Number) = Protons; A (Mass Number) = Protons + Neutrons.

• Cation: Positive charge, loses electrons.
• Anion: Negative charge, gains electrons.

Radiation and Energy Calculations

Frequency: f = c / λ (where c = 3 × 10⁸ m/s).

Planck's Constant: E = h × f (h = 6.63 × 10^-34 J·s).

Energy Levels: ΔE = E_f - E_i = -K / n².

• Absorption: Inf → Sup (Energy +).
• Emission: Sup → Inf (Energy -).

Isotopes and Quantum Numbers

Isotopes: Same atomic number (Z) but different atomic mass (A).

• n (Principal): Energy level (1, 2, 3...).
• l (Angular Momentum): Orbital shape (0 to n-1).
• m_l (Magnetic): Orientation (-l to +l).
• m_s (Spin): Electron spin (+½, -½).

Orbital Types

• l = 0: s²
• l = 1: p⁶
• l = 2: d¹⁰
• l = 3: f¹⁴

Electron Configuration

Möller Rule (n + l): Used to determine orbital energy levels.

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², 4f¹⁴, 5d¹⁰, 6p⁶, 7s², 5f¹⁴, 6d¹⁰, 7p⁶, 6f¹⁴, 7d¹⁰, 7f¹⁴.

Periodic Table Trends

Atomic Radius:

• Group: Increases downward (more electron shells).
• Period: Increases right to left (greater nuclear attraction).

Ionization Energy:

• Group: Increases upward.
• Period: Increases left to right.

Electronegativity and Affinity: Follow trends similar to ionization energy; measures the ability to attract shared electrons in covalent bonds.