Chapter 2 - Atoms and the Periodic Table - Problems - Page 62: 2.27

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a. Fluorine (F) — Atomic number: 9 Valence electrons: 7 Valence electron configuration: 2s² 2p⁵ Fluorine is in period 2, so its valence shell is n = 2 b. Krypton (Kr) — Atomic number: 36 Valence electrons: 8 Valence electron configuration: 4s² 4p⁶ Krypton is in period 4, and it's a noble gas with a full valence shell c. Magnesium (Mg) — Atomic number: 12 Valence electrons: 2 Valence electron configuration: 3s² Magnesium is in period 3, so its valence shell is n = 3 d. Germanium (Ge) — Atomic number: 32 Valence electrons: 4 Valence electron configuration: 4s² 4p² Germanium is in period 4, and its 3d electrons are not counted as valence electrons for main group chemistry