In 1893, Alfred Werner showed that the number of atoms or groups associated with a central atom (the “coordination number”) is often 4 or 6; other coordination numbers up to a maximum of 8 were known, but less frequent.
1893年阿爾弗雷德·維爾納發現，與中央連接的原子或官能基的數目（「配位數」）通常是4或者6，最高可以是8，不過罕有發生。