The 18 Fule Rule References:Gray:chapter 5 OGC:chapter 8 XIV-1
The 18 Electron Rule References: Gray: chapter 5 OGC: chapter 8 XIV-1
Element Groups Alkali metals Inert or Noble gases Alkali earths Halogens I He g Transition metals B C N F Ne Al Si P S Ci Ar Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr b Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Xe Ba La Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Lanthanides Actinides XIV-2
H L i N a K R b C s F r B e M g C a S r B a R a S c Y L a A c T i Z r H f V N b T a C r M o W M n T c R e F e R u O s C o R h I r N i P d P t C u A g A u Z n C d H g B A l G a I n T l C S i G e S n P b N P A s S b B i O S S e T e P o F C l B r I A t H e N e A r K r X e R n C e P r N d P m S m E u G d T b D y H o E r T m Y b L u T h P a U N p P u A m C m B k C f E s F m M d N o L r Element Groups Alkali metals Transition metals Alkali earths Halogens Inert or Noble gases Lanthanides Actinides XIV-2
The Chemists Geoffrey Wilkinson E.O.Fischer Nobel Prize,chemistry,1973 "For their pioneering work,performed independently,on the chemistry of the organometallic,so called sandwich compounds" XIV-3
Geoffrey Wilkinson E. O. Fischer Nobel Prize, chemistry, 1973 “For their pioneering work, performed independently, on the chemistry of the organometallic, so called sandwich compounds” The Chemists XIV-3
18 e Rule for Transition Elements Remember the dot structure for CO? -1 +1 C∷O:> :C≡O:> ∷C=O: Consider Cr,a transition element: Chromium:[Ar](4s)2(3d)4-6 valence e Like most transition elements,Cr needs 18 e in its shell. O 12 e from CO's +6 e from Cr =18 total e;formula is Cr(CO)e Dot structures can predict C≡O: molecules;if we are given :O蕊C8 an exception,we can explain its existence,and figure out some of its chemical properties. 4
Cr 18 e- Rule for Transition Elements • Remember the dot structure for CO? C O C O • Consider Cr, a transition element: Chromium: [Ar] (4s)2 (3d)4 → 6 valence e- • Like most transition elements, Cr needs 18 e- in its shell. O C C O C O C O 12 e- from COʼs + 6 e- from Cr = 18 total e- ; formula is Cr(CO)6 Dot structures can predict molecules; if we are given an exception, we can explain its existence, and figure out some of its chemical properties. C O -1 +1 XIV-4
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-5
Using the 18 e- rule • Given that H2Fe(CO)x exists, what does x equal? Iron: [Ar] (4s)2 (3d)6 → 8 valence eHydrogen: (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