Editing Lanthanide (section)

===Lanthanide oxidation states===
{| class="wikitable collapsible collapsed" style="font-size:95%;"
|+ Ionization energies and reduction potentials of the elements
![[Chemical element]]!![[Lanthanum|La]]!![[Cerium|Ce]]!![[praseodymium|Pr]]!![[neodymium|Nd]]!![[promethium|Pm]]!![[samarium|Sm]]!![[europium|Eu]]!![[gadolinium|Gd]]!![[terbium|Tb]]!![[dysprosium|Dy]]!![[holmium|Ho]]!![[erbium|Er]]!![[thulium|Tm]]!![[ytterbium|Yb]]!![[lutetium|Lu]]
|-
| [[Atomic number]]
|57||58||59||60||61||62||63||64||65||66||67||68||69||70||71
|-
| [[electron configuration]]<br> above [Xe] core||'''4f<sup>0</sup>5d<sup>1</sup>'''6s<sup>2</sup>||'''4f<sup>1</sup>5d<sup>1</sup>'''6s<sup>2</sup>||4f<sup>3</sup>6s<sup>2</sup>||4f<sup>4</sup>6s<sup>2</sup>|| 4f<sup>5</sup>6s<sup>2</sup>||4f<sup>6</sup>6s<sup>2</sup>||4f<sup>7</sup>6s<sup>2</sup>||'''4f<sup>7</sup>5d<sup>1</sup>'''6s<sup>2</sup>||4f<sup>9</sup>6s<sup>2</sup>||4f<sup>10</sup>6s<sup>2</sup>||4f<sup>11</sup>6s<sup>2</sup>||4f<sup>12</sup>6s<sup>2</sup>||4f<sup>13</sup>6s<sup>2</sup>||4f<sup>14</sup>6s<sup>2</sup>||4f<sup>14</sup>5d<sup>1</sup>6s<sup>2</sup>
|-
|E° Ln<sup>4+</sup>/Ln<sup>3+</sup>
|  ||1.72||  3.2|| ||  ||  ||  ||  ||  3.1|| ||  ||  ||  ||  ||
|-
|E° Ln<sup>3+</sup>/Ln<sup>2+</sup>
|  ||  ||  ||−2.6||  ||−1.55||−0.35||  ||  ||−2.5||  ||  ||−2.3||−1.05||
|-
|E° Ln<sup>3+</sup>/Ln           
| −2.38||−2.34||−2.35||−2.32||−2.29||−2.30||−1.99||−2.28||−2.31||−2.29||−2.33||−2.32||−2.32||−2.22||−2.30
|-
|1st Ionization energy<br> (kJ·mol<sup>−1</sup>)
|538||541||522||530||536||542||547||595||569||567||574||581||589||603||513
|-
|2nd Ionization energy<br> (kJ·mol<sup>−1</sup>)
|1067||1047||1018||1034||1052||1068||1085||1172||1112||1126||1139||1151||1163||1175||1341
|-
|1st + 2nd Ionization energy<br> (kJ·mol<sup>−1</sup>)
|1605||1588||1540||1564||1588||1610||1632||1767||1681||1693||1713||1732||1752||1778||1854
|-
|3rd Ionization energy<br> (kJ·mol<sup>−1</sup>)
|1850||1940||2090||2128||2140||2285||2425||1999||2122||2230||2221||2207||2305||2408||2054
|-
|1st + 2nd + 3rd Ionization energy<br> (kJ·mol<sup>−1</sup>)
|3455||3528||3630||3692||3728||3895||4057||3766||3803||3923||3934||3939||4057||4186||3908
|-
|4th Ionization energy<br> (kJ·mol<sup>−1</sup>)
|4819||3547||3761||3900||3970||3990||4120||4250||3839||3990||4100||4120||4120||4203||4370
|}
The ionization energies for the lanthanides can be compared with aluminium. In aluminium the sum of the first three ionization energies is 5139 kJ·mol<sup>−1</sup>, whereas the lanthanides fall in the range 3455 – 4186 kJ·mol<sup>−1</sup>. This correlates with the highly reactive nature of the lanthanides.

The sum of the first two ionization energies for europium, 1632 kJ·mol<sup>−1</sup> can be compared with that of barium 1468.1 kJ·mol<sup>−1</sup> and europium's third ionization energy is the highest of the lanthanides. The sum of the first two ionization energies for ytterbium are the second lowest in the series and its third ionization energy is the second highest. The high third ionization energy for Eu and Yb correlate with the half filling 4f<sup>7</sup> and complete filling 4f<sup>14</sup> of the 4f subshell, and the stability afforded by such configurations due to exchange energy.<ref name=CottonSA2006/> Europium and ytterbium form salt like compounds with Eu<sup>2+</sup> and Yb<sup>2+</sup>, for example the salt like dihydrides.<ref name="Fukai"/> Both europium and ytterbium dissolve in liquid ammonia forming solutions of Ln<sup>2+</sup>(NH<sub>3</sub>)<sub>x</sub> again demonstrating their similarities to the alkaline earth metals.<ref name = "Greenwood&Earnshaw"/>

The relative ease with which the 4th electron can be removed in cerium and (to a lesser extent praseodymium) indicates why Ce(IV) and Pr(IV) compounds can be formed, for example CeO<sub>2</sub> is formed rather than Ce<sub>2</sub>O<sub>3</sub> when cerium reacts with oxygen. Also Tb has a well-known IV state, as removing the 4th electron in this case produces a half-full 4f<sup>7</sup> configuration.

The additional stable valences for Ce and Eu mean that their abundances in rocks sometimes varies significantly relative to the other rare earth elements: see [[cerium anomaly]] and [[europium anomaly]].