Transition metals electronic configuration

Moreover, the analysis of the optical spectra of transition metal and rare earth ions is very illnstrative, as they present qnite different features due to their particular electronic configurations transition metal ions have optically active unfilled outer 3d shells, while rare earth ions have unfilled optically active 4f electrons screened by outer electroiuc filled shells. Because of these unfilled shells, both kind of ion are usually called paramagnetic ions. 

The same reasoning may hold for the virtual absence of transition metal dicarbides with (C2) anions. On the other hand, stable multinary compounds in A-M-(BNx), AE-M-(BNx), or Ln-M-(BNx) systems can exist with an electron-rich transition metal (M), similar to the known ternary dicarbides AM(C2) with A=alkali and M = Pd, Pt [25]. In these cases the valence electrons provided from A or AE metals fill the bonding (BNx)" or (C2) levels, and the transition metal retains an approximate d ° configuration. 

Transition metal ions have an incompletely filled d-shell, i.e. their electron configuration is d". The optically active electrons are thus bound to central potential as well as experiencing crystal field potential, and are not shielded by outer electrons. Most transition metal ions are multi-valent. Mainly the number of 3d electrons and the crystal field determine their optical properties. Thus the groups below have similar optical behavior ... 

The alkali metals are the most chemically active metals. Alkaline earth metals are second in reactivity. Elements in the same family have the same outermost electron configuration. Alkali metals have one outermost electron that is easily transferred to needy atoms. Alkaline earth metals have two outermost electrons to share or transfer. The transition metals are the least active. 

The type of bonding found in metals is quite different from that in other crystals. As we compare the various main group and transition metals in the periodic table we see only small differences in electronegativity. So, there is little tendency for ionic bonding in metals. The electronic configurations of metal atoms, even in the transition metals, do not have nearly-filled subshells, so there is little tendency to form covalent bonds by sharing electrons to achieve a stable octet. The familiar classical models of chemical bonding (see Chapter 3) do not extend to metals. 

In organometalfic compounds, most p-electrons of transition metals conform to an empirical rule called the 18-electron rule. This rule assumes that the metal atom accepts from its ligands the number of electrons needed in order for it to attain the electronic configuration of the next noble gas. It assumes that the valence shells of the metal atom will contain 18 electrons. Thus, the sum of the number of d electrons plus the number of electrons suppfied by the figands will be 18. Ferrocene, for example, has 6 d electrons from Fe(II), plus 2x6 electrons from the two 5-membered rings, for a total of 18. (There are exceptions to this rule, however.)... 

Characteristic of d-block transition elements. Covalent interaction between 2p orbitals of ligand and valence orbitals, (n-l)d, ns and np of metal (Chapter 6). Involvement of metal d-orbitals important. 18-Electron configuration of metal commonly associated with kinetic stability. ... 

Copper differs in its chemistry from the earlier members of the first transition series. The outer electronic configuration contains a completely-filled set of d-orbitals and. as expected, copper forms compounds where it has the oxidation state -)-l. losing the outer (4s) electron and retaining all the 3d electrons. However, like the transition metals preceding it, it also shows the oxidation state +2 oxidation states other than -l-l and - -2 are unimportant. 

Not all ligands use just two electrons to bond to transition metals Chromium has the electron configuration [Ar]4s 3rf (6 valence electrons) and needs 12 more to satisfy the 18 electron rule In the compound (benzene)tricarbonylchromium 6 of these 12 are the tt elec Irons of the benzene ring the remammg 6 are from the three carbonyl ligands... 

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