Using the 18e rule Given that H2Fe(CO)x exists,what does x equal? Iron:[Ar](4s)2(3d)6 -8 valence e Hydrogen:(1s)1 →1 valence e Fe wants to have 18 e,because it's a transition element,but it only has 8.The H's give 2 e,but we still need 8 electrons. Since each CO supplies 2 e,there must be 4 CO's: O H2Fe(CO)4 Ⅲ O CO: R. H -H OC: XIV-5Using the 18 e- rule • Given that H2Fe(CO)x exists, what does x equal? Iron: [Ar] (4s)2 (3d)6 → 8 valence e￾Hydrogen: (1s)1 → 1 valence e- • Fe wants to have 18 e- , because itʼs a transition element, but it only has 8. The Hʼs give 2 e- , but we still need 8 electrons. Since each CO supplies 2 e- , there must be 4 COʼs: C O C O H H H2Fe(CO)4 Fe C O H H C O Fe XIV-5