Search results
Results From The WOW.Com Content Network
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element.For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory.
The spectrochemical series is an empirically-derived list of ligands ordered by the size of the splitting Δ that they produce. It can be seen that the low-field ligands are all π-donors (such as I − ), the high field ligands are π-acceptors (such as CN − and CO), and ligands such as H 2 O and NH 3 , which are neither, are in the middle.
The spectral lines are grouped into series according to n′. Lines are named sequentially starting from the longest wavelength/lowest frequency of the series, using Greek letters within each series. For example, the 2 → 1 line is called "Lyman-alpha" (Ly-α), while the 7 → 3 line is called "Paschen-delta" (Pa-δ).
Spectrochemistry is the application of spectroscopy in several fields of chemistry. It includes analysis of spectra in chemical terms, and use of spectra to derive the structure of chemical compounds, and also to qualitatively and quantitively analyze their presence in the sample.
The spectrochemical series is an empirically-derived list of ligands ordered by the size of the splitting Δ that they produce (small Δ to large Δ; see also this table): I − < Br − < S 2− < SCN − (S–bonded) < Cl − < NO 3 − < N 3 − < F − < OH − < C 2 O 4 2− < H 2 O < NCS − (N–bonded) < CH 3 CN < py < NH 3 < en < 2,2 ...
In 1890, Rydberg proposed on a formula describing the relation between the wavelengths in spectral lines of alkali metals. [2]: v1:376 He noticed that lines came in series and he found that he could simplify his calculations using the wavenumber (the number of waves occupying the unit length, equal to 1/λ, the inverse of the wavelength) as his unit of measurement.
This ordering of ligands is almost invariable for all metal ions and is called spectrochemical series. For complexes with a tetrahedral surrounding, the d-orbitals again split into two sets, but this time in reverse order: 2 orbitals of low energy: d z 2 and d x 2 −y 2 and; 3 orbitals of high energy: d xy, d xz and d yz.
Low-spin [Fe(NO 2) 6] 3− crystal field diagram. The Δ splitting of the d orbitals plays an important role in the electron spin state of a coordination complex. Three factors affect Δ: the period (row in periodic table) of the metal ion, the charge of the metal ion, and the field strength of the complex's ligands as described by the spectrochemical series.