# Relativistic quantum chemistry

- Relativistic quantum chemistry
**Relativistic quantum chemistry** is a branch of quantum chemistry that applies relativistic mechanics, and, in particular the Dirac equation or an approximation to it (e.g., at the lowest level, the Pauli equation), to electron dynamics and chemical bonding, especially the behavior of the heavier elements of the periodic table.

Many of the chemical and physical differences between the 6th Row (Cs-Rn) and the 5th Row (Rb-Xe) arise from the larger **relativistic effects** for the former. These relativistic effects are particularly large for gold and its neighbours, platinum and mercury.

Some of the phenomena commonly attributed to relativistic effects are:

* The low melting point of mercury

* The stability of the Hg_{2}^{2+} ion

* The stability of Mercury(IV) fluoride

* Aurophilicity

* The stability of the gold anion, Au^{−}, in compounds such as CsAu

* The color of gold

* The preference for higher oxidation states among metals in the third transition series, W-Au

* The inert pair effect in thalium, lead, and bismuth, which leads to lower oxidation states

* The crystal structure of lead, which is face-centered cubic instead of diamond-like

* The striking similarity between zirconium and hafnium

* The stability of the uranyl cation, as well as other high oxidation states in the early actinides (Pa-Am)

* The small atomic radii of francium and radium

* About 10% of the lanthanide contraction is attributed to relativistic effects

**References**

* P. A. Christiansen; W. C. Ermler; K. S. Pitzer. Relativistic Effects in Chemical Systems. "Annual view of Physical Chemistry" **1985**, "36", 407-432. doi|10.1146/annurev.pc.36.100185.002203

* Pekka Pyykko. Relativistic effects in structural chemistry. "Chem. Rev." **1988**, "88", 563-594.

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