This paper investigates the half-metallic behavior of full-Heusler alloys based on Co, Fe, Rh, and Ru using the full-potential screened Korringa-Kohn-Rostoker method. It shows that these alloys exhibit half-metallic behavior with a small spin-down band gap due to localized states at the Co (Fe, Rh, or Ru) sites, unlike half-Heusler alloys. The total spin magnetic moment per unit cell (M_t) scales with the total number of valence electrons (Z_t) following the rule M_t = Z_t - 24. This behavior is explained using group theory, showing that the spin-down band contains exactly 12 electrons. The study also discusses deviations from this rule and differences compared to half-Heusler alloys. The paper analyzes the electronic structure of Co₂MnZ compounds, showing that they follow the Slater-Pauling behavior with a spin-down pseudogap. It also examines other full-Heusler compounds, including those with less than 24 valence electrons, and discusses the possibility of achieving a total spin moment of 6 μB for compounds with 30 valence electrons. The study concludes that full-Heusler alloys exhibit Slater-Pauling behavior and that the half-metallic properties are due to the specific arrangement of atoms and their electronic structure.This paper investigates the half-metallic behavior of full-Heusler alloys based on Co, Fe, Rh, and Ru using the full-potential screened Korringa-Kohn-Rostoker method. It shows that these alloys exhibit half-metallic behavior with a small spin-down band gap due to localized states at the Co (Fe, Rh, or Ru) sites, unlike half-Heusler alloys. The total spin magnetic moment per unit cell (M_t) scales with the total number of valence electrons (Z_t) following the rule M_t = Z_t - 24. This behavior is explained using group theory, showing that the spin-down band contains exactly 12 electrons. The study also discusses deviations from this rule and differences compared to half-Heusler alloys. The paper analyzes the electronic structure of Co₂MnZ compounds, showing that they follow the Slater-Pauling behavior with a spin-down pseudogap. It also examines other full-Heusler compounds, including those with less than 24 valence electrons, and discusses the possibility of achieving a total spin moment of 6 μB for compounds with 30 valence electrons. The study concludes that full-Heusler alloys exhibit Slater-Pauling behavior and that the half-metallic properties are due to the specific arrangement of atoms and their electronic structure.