分子量计算器 — 公式

Effective Nuclear Charge

Formula

Z_eff = Z − σ

Where:

  • Z_eff = effective nuclear charge felt by valence electron
  • Z = atomic number (total protons)
  • σ = shielding constant (from Slater's rules)

    • Inner electrons shield outer electrons from the full nuclear charge. Z_eff increases across a period (more protons, similar shielding) and stays roughly constant down a group.

    计算示例

    Sodium (Z = 11) with shielding constant σ = 8.8 for the 3s electron.

    1. Z_eff = Z - σ
    2. Z_eff = 11 - 8.8
    3. Z_eff = 2.2
    4. The 3s electron feels an effective charge of +2.2