Editing Actinide (section)

== Compounds ==

=== Oxides and hydroxides ===
{| Class = "wikitable collapsible collapsed" style="text-align:center;"
|+ Oxides of actinides<ref name="Himiya aktiniya" /><ref name="Himiya neptuniya" /><ref name="Himiya protaktiniya">{{cite book|author=E.S. Palshin|title=Analytical chemistry of protactinium|place=Moscow|publisher=Nauka|year=1968}}</ref><ref>Myasoedov, p. 88</ref><ref name="Tablitsa soedineniy" />
|-
! rowspan="2"|[[Chemical compounds|Compound]]
! rowspan="2"|Color
! rowspan="2"|Crystal symmetry, type
! colspan="3"|Lattice constants, Å
! rowspan="2"|Density, g/cm<sup>3</sup>
! rowspan="2"|Temperature, °C
|-
!''a''
!''b''
!''c''
|-
| Ac<sub>2</sub>O<sub>3</sub>|| White|| Hexagonal, La<sub>2</sub>O<sub>3</sub>|| 4.07 ||-|| 6.29|| 9.19|| –
|-
| PaO<sub>2</sub>||-|| Cubic, CaF<sub>2</sub>|| 5.505 ||-||-||-||-
|-
| Pa<sub>2</sub>O<sub>5</sub>|| White|| cubic, CaF<sub>2</sub><br /> Cubic<br /> Tetragonal<br /> Hexagonal<br /> Rhombohedral <br />Orthorhombic|| 5.446<br /> 10.891<br /> 5.429<br /> 3.817<br /> 5.425<br /> 6.92|| -<br /> -<br /> -<br /> -<br /> -<br /> 4.02|| -<br /> 10.992<br /> 5.503<br /> 13.22<br /> -<br /> 4. 18 ||-|| 700<br /> 700–1100<br /> 1000<br /> 1000–1200<br /> 1240–1400<br /> –
|-
| ThO<sub>2</sub>|| Colorless|| Cubic|| 5.59 ||-||-|| 9.87|| –
|-
| UO<sub>2</sub>|| Black-brown|| Cubic|| 5.47 ||-||-|| 10.9|| –
|-
| NpO<sub>2</sub>|| Greenish-brown|| Cubic, CaF<sub>2</sub>|| 5.424 ||-||-|| 11.1|| –
|-
| PuO|| Black|| Cubic, NaCl|| 4.96 ||-||-|| 13.9|| –
|-
| PuO<sub>2</sub>|| Olive green|| Cubic|| 5.39 ||-||-|| 11.44|| –
|-
| Am<sub>2</sub>O<sub>3</sub>|| Red-brown<br /> Red-brown|| Cubic, Mn<sub>2</sub>O<sub>3</sub><br /> Hexagonal, La<sub>2</sub>O<sub>3</sub>|| 11.03<br /> 3.817 ||-||-<br /> 5.971|| 10.57<br /> 11.7|| –
|-
| AmO<sub>2</sub>|| Black|| Cubic, CaF<sub>2</sub>|| 5.376 ||-||-||-||-
|-
| Cm<sub>2</sub>O<sub>3</sub>|| White<ref>According to other sources, cubic sesquioxide of curium is olive-green. See {{cite web|url = http://www.xumuk.ru/encyklopedia/2248.html|title=Соединения curium site XuMuK.ru|language = ru|access-date =11 July 2010| archive-url= https://web.archive.org/web/20100818211138/http://www.xumuk.ru/encyklopedia/2248.html|archive-date=18 August 2010|url-status=live}}</ref><br /> -<br /> -|| Cubic, Mn<sub>2</sub>O<sub>2</sub><br /> Hexagonal, LaCl<sub>3</sub><br /> Monoclinic, Sm<sub>2</sub>O<sub>3</sub>|| 11.01<br /> 3.80<br /> 14.28|| -<br /> -<br /> 3.65|| -<br /> 6<br /> 8.9|| 11.7|| –
|-
| CmO<sub>2</sub>|| Black|| Cubic, CaF<sub>2</sub>|| 5.37 ||-||-||-||-
|-
| Bk<sub>2</sub>O<sub>3</sub>|| Light brown|| Cubic, Mn<sub>2</sub>O<sub>3</sub>|| 10.886||-||-||-||-
|-
| BkO<sub>2</sub>|| Red-brown|| Cubic, CaF<sub>2</sub>|| 5.33 ||-||-||-||-
|-
| Cf<sub>2</sub>O<sub>3</sub><ref>The atmosphere during the synthesis affects the lattice parameters, which might be due to non-stoichiometry as a result of oxidation or reduction of the trivalent californium. Main form is the cubic oxide of californium(III).</ref>|| Colorless <br />Yellowish<br /> -|| Cubic, Mn<sub>2</sub>O<sub>3</sub><br /> Monoclinic, Sm<sub>2</sub>O<sub>3</sub><br /> Hexagonal, La<sub>2</sub>O<sub>3</sub>|| 10.79<br /> 14.12<br /> 3.72|| -<br /> 3.59<br /> -|| -<br /> 8.80<br /> 5.96 ||-||-
|-
| CfO<sub>2</sub>|| Black|| Cubic|| 5.31 ||-||-||-||-
|-
| Es<sub>2</sub>O<sub>3</sub>||-|| Cubic, Mn<sub>2</sub>O<sub>3</sub><br /> Monoclinic <br /> Hexagonal, La<sub>2</sub>O<sub>3</sub>|| 10.07<br /> 14.1<br /> 3.7|| -<br /> 3.59<br /> -|| -<br /> 8.80<br /> 6 ||-||-
|}

{| class="wikitable collapsible collapsed" style="text-align:center"
|+Approximate colors of actinide oxides<br />(most stable are bolded)<ref name=g1268>Greenwood, p. 1268</ref>
! Oxidation state
| 89 || 90 || 91 || 92 || 93 || 94 || 95 || 96 || 97 || 98 ||99
|-
| +3||'''Ac<sub>2</sub>O<sub>3</sub>'''|| || || ||
|bgcolor=black| <span style="color:white;">Pu<sub>2</sub>O<sub>3</sub></span>
| style="background:#fa7;"| Am<sub>2</sub>O<sub>3</sub>
| '''Cm<sub>2</sub>O<sub>3</sub>'''
| style="background:#dfe111;"| Bk<sub>2</sub>O<sub>3</sub>
| style="background:#cf0;"| '''Cf<sub>2</sub>O<sub>3</sub>'''
| '''Es<sub>2</sub>O<sub>3</sub>'''
|-
| +4|| || '''ThO<sub>2</sub>'''
|bgcolor=black| <span style="color:white;">PaO<sub>2</sub></span>
| style="background:#765538;"| <span style="color:white;">UO<sub>2</sub></span>
| style="background:#616639;"| '''NpO<sub>2</sub>'''
| style="background:#e1bb11;"| '''PuO<sub>2</sub>'''
|bgcolor=black| <span style="color:white;">'''AmO<sub>2</sub>'''</span>
|bgcolor=black| <span style="color:white;">CmO<sub>2</sub></span>
|bgcolor=brown| '''BkO<sub>2</sub>'''
|bgcolor=black| <span style="color:white;">CfO<sub>2</sub></span>
|
|-
| +5|| ||
| '''Pa<sub>2</sub>O<sub>5</sub>'''
|bgcolor=black| <span style="color:white;">U<sub>2</sub>O<sub>5</sub></span>
| style="background:#765538;"| <span style="color:white;">Np<sub>2</sub>O<sub>5</sub></span>
|| || || || || ||
|-
| +5,+6 || || ||
| style="background:#0d5e35;"| <span style="color:white;">'''U<sub>3</sub>O<sub>8</sub>'''</span>
|| || || || || || ||
|-
|| +6|| || ||
| style="background:#f89d1a;"| UO<sub>3</sub>
|| || || || || || ||
|}

{| Class = "wikitable collapsible" style="text-align: center"
|+ Dioxides of some actinides
|-
|  style="background:lightblue; text-align:left;"|[[Chemical formula]]
| [[Thorium dioxide|ThO<sub>2</sub>]]|| [[Protactinium(IV) oxide|PaO<sub>2</sub>]]|| [[Uranium dioxide|UO<sub>2</sub>]]|| [[Neptunium(IV) oxide|NpO<sub>2</sub>]]|| [[Plutonium(IV) oxide|PuO<sub>2</sub>]]|| [[Americium dioxide|AmO<sub>2</sub>]]|| CmO<sub>2</sub>|| BkO<sub>2</sub>|| CfO<sub>2</sub>
|-
|  style="background:lightblue; text-align:left;"|[[CAS Number]]
| 1314-20-1|| 12036-03-2|| 1344-57-6|| 12035-79-9|| 12059-95-9|| 12005-67-3|| 12016-67-0|| 12010-84-3|| 12015–10–0
|-
|  style="background:lightblue; text-align:left;"|[[Molar mass]]
| 264.04 || 263.035 || 270.03 || 269.047 || 276.063 || 275.06 || 270–284**|| 279.069 || 283.078
|-
|  style="background:lightblue; text-align:left;"|[[Melting point]]<ref>{{cite book|author1=L.R. Morss |author2=Norman M. Edelstein|author3=Jean Fuger|title=The Chemistry of the Actinide and Transactinide Elements (Set Vol.1–6)|url=https://books.google.com/books?id=9vPuV3A0UGUC&pg=PA2139|year=2011|publisher=Springer|isbn=978-94-007-0210-3|page=2139}}</ref>
| 3390&nbsp;°C||||2865&nbsp;°C||2547&nbsp;°C||2400&nbsp;°C||2175&nbsp;°C|| || ||
|-
|  style="background:lightblue; text-align:left;"|Crystal structure
| Colspan = "9"|[[File:CaF2 polyhedra.png|250px]]<br />'''An'''<sup>4+</sup>: <span style="color:silver; background:silver;">__</span>&nbsp;&nbsp;/&nbsp;&nbsp;O<sup>2−</sup>: <span style="color:#9c0; background:#9c0;">__</span>
|-
|  style="background:lightblue; text-align:left;"|[[Space group]]
| Colspan = "9"|Fm{{overline|3}}m
|-
|  style="background:lightblue; text-align:left;"|[[Coordination number]]
| Colspan = "9" |'''An'''[8], O[4]
|}
: <small>'''An''' – actinide <br />**Depending on the isotopes</small>

Some actinides can exist in several oxide forms such as An<sub>2</sub>O<sub>3</sub>, AnO<sub>2</sub>, An<sub>2</sub>O<sub>5</sub> and AnO<sub>3</sub>. For all actinides, oxides AnO<sub>3</sub> are [[Amphoterism|amphoteric]] and An<sub>2</sub>O<sub>3</sub>, AnO<sub>2</sub> and An<sub>2</sub>O<sub>5</sub> are basic, they easily react with water, forming bases:<ref name=g222 />

: An<sub>2</sub>O<sub>3</sub> + 3 H<sub>2</sub>O → 2 An(OH)<sub>3</sub>.
These bases are poorly soluble in water and by their activity are close to the [[hydroxide]]s of rare-earth metals.<ref name=g222 />
Np(OH)<sub>3</sub> has not yet been synthesized, [[Plutonium(III) hydroxide|Pu(OH)<sub>3</sub>]] has a blue color while [[Americium(III) hydroxide|Am(OH)<sub>3</sub>]] is pink and [[Curium(III) hydroxide|Cm(OH)<sub>3</sub>]] is colorless.<ref name="Tananaev">{{cite book|last1=Krivovichev|first1=Sergei|last2=Burns|first2=Peter|last3=Tananaev|first3=Ivan|title=Structural Chemistry of Inorganic Actinide Compounds|publisher=Elsevier|chapter=Chapter 3|isbn=978-0-08-046791-7|year=2006|pages=67–78|chapter-url=https://books.google.com/books?id=mV-phntexBQC&pg=PA67}}</ref> Bk(OH)<sub>3</sub> and Cf(OH)<sub>3</sub> are also known, as are tetravalent hydroxides for Np, Pu and Am and pentavalent for Np and Am.<ref name="Tananaev" />

The strongest base is of actinium. All compounds of actinium are colorless, except for black [[actinium sulfide]] (Ac<sub>2</sub>S<sub>3</sub>).<ref name="g222" /> Dioxides of tetravalent actinides crystallize in the [[cubic system]], same as in [[calcium fluoride]].

Thorium reacting with oxygen exclusively forms the dioxide:
: <chem>Th{} + O2 ->[\ce{1000^\circ C}] \overbrace{ThO2}^{Thorium~dioxide}</chem>

Thorium dioxide is a refractory material with the highest melting point among any known oxide (3390&nbsp;°C).<ref name="g1268" /> Adding 0.8–1% ThO<sub>2</sub> to tungsten stabilizes its structure, so the doped filaments have better mechanical stability to vibrations. To dissolve ThO<sub>2</sub> in acids, it is heated to 500–600&nbsp;°C; heating above 600&nbsp;°C produces a very resistant to acids and other reagents form of ThO<sub>2</sub>. Small addition of fluoride ions [[Catalyst|catalyses]] dissolution of thorium dioxide in acids.

Two protactinium oxides have been obtained: PaO<sub>2</sub> (black) and Pa<sub>2</sub>O<sub>5</sub> (white); the former is isomorphic with ThO<sub>2</sub> and the latter is easier to obtain. Both oxides are basic, and Pa(OH)<sub>5</sub> is a weak, poorly soluble base.<ref name=g222 />

Decomposition of certain salts of uranium, for example UO<sub>2</sub>(NO<sub>3</sub>)·6H<sub>2</sub>O in air at 400&nbsp;°C, yields orange or yellow UO<sub>3</sub>.<ref name="g1268" /> This oxide is amphoteric and forms several hydroxides, the most stable being [[uranyl hydroxide]] UO<sub>2</sub>(OH)<sub>2</sub>. Reaction of uranium(VI) oxide with hydrogen results in uranium dioxide, which is similar in its properties with ThO<sub>2</sub>. This oxide is also basic and corresponds to the uranium hydroxide U(OH)<sub>4</sub>.<ref name=g222 />

Plutonium, neptunium and americium form two basic oxides: An<sub>2</sub>O<sub>3</sub> and AnO<sub>2</sub>. Neptunium trioxide is unstable; thus, only Np<sub>3</sub>O<sub>8</sub> could be obtained so far. However, the oxides of plutonium and neptunium with the chemical formula AnO<sub>2</sub> and An<sub>2</sub>O<sub>3</sub> are well characterized.<ref name=g222 />

=== Salts ===

{| Class = "wikitable collapsible" style="text-align: center"
|+ Trichlorides of some actinides<ref name=g1270>Greenwood, p. 1270</ref>
|-
! style="background:lightblue; text-align:left;"|[[Chemical formula]]
| AcCl<sub>3</sub>|| UCl<sub>3</sub>|| NpCl<sub>3</sub>|| PuCl<sub>3</sub>|| AmCl<sub>3</sub>|| CmCl<sub>3</sub>|| BkCl<sub>3</sub>|| CfCl<sub>3</sub>
|-
! style="background:lightblue; text-align:left;"|[[CAS-number]]
| 22986-54-5|| 10025-93-1|| 20737-06-8|| 13569-62-5|| 13464-46-5|| 13537-20-7|| 13536-46-4|| 13536–90–8
|-
! style="background:lightblue; text-align:left;"|[[Molar mass]]
| 333.386 || 344.387 || 343.406 || 350.32 || 349.42 || 344–358**|| 353.428 || 357.438
|-
! style="background:lightblue; text-align:left;"|[[Melting point]]
||| 837&nbsp;°C||800&nbsp;°C||767&nbsp;°C||715&nbsp;°C||695&nbsp;°C||603&nbsp;°C||545&nbsp;°C
|-
! style="background:lightblue; text-align:left;"|[[Boiling point]]
||| 1657&nbsp;°C||||1767&nbsp;°C||850&nbsp;°C|| || ||
|-
! style="background:lightblue; text-align:left;"|Crystal structure
| Colspan = "8"|[[File:UCl3 without caption.png|250px|The crystal structure of uranium trichloride]]<br />'''An'''<sup>3+</sup>: <span style="color:silver; background:silver;">__</span>&nbsp;&nbsp;/&nbsp;&nbsp;Cl<sup>−</sup>: <span style="color:#0f0; background:#0f0;">__</span>
|-
! style="background:lightblue; text-align:left;"|[[Space group]]
| Colspan = "8"|P6<sub>3</sub>/m
|-
! style="background:lightblue; text-align:left;"|[[Coordination number]]
| Colspan = "8" |'''An'''*[9], Cl [3]
|-
! style="background:lightblue; text-align:left;"|Lattice constants
| ''a'' = 762 [[picometres|pm]]<br /> ''c'' = 455 pm|| ''a'' = 745.2 pm<br /> ''c'' = 432.8 pm|| || ''a'' = 739.4 pm<br /> ''c'' = 424.3 pm|| ''a'' = 738.2 pm<br /> ''c'' = 421.4 pm|| ''a'' = 726 pm<br /> ''c'' = 414 pm|| ''a'' = 738.2 pm<br /> ''c'' = 412.7 pm|| ''a'' = 738 pm <br /> ''c'' = 409 pm
|}
:<small> *'''An''' – actinide <br />**Depending on the isotopes</small>

{| Class = "wikitable collapsible collapsed" style="text-align: center"
|+ Actinide fluorides<ref name="Himiya neptuniya" /><ref name="Himiya protaktiniya" /><ref name="Tablitsa soedineniy">{{cite web|url=http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/01_osnovnye_svoystva_neorganicheskikh_organicheskikh_i_elementoorganicheskikh_soedineniy|title=Таблица Inorganic and Coordination compounds|language = ru|access-date =11 July 2010}}</ref><ref name=g1270 /><ref>Myasoedov, pp. 96–99</ref>
|-
! Rowspan = "2"|Compound
! rowspan="2"|Color
! rowspan="2"|Crystal symmetry, type
! colspan="3"|Lattice constants, Å
! rowspan="2"|Density, g/cm<sup>3</sup>
|-
!''a''
!''b''
!''c''
|-
| AcF<sub>3</sub>|| White|| Hexagonal, LaF<sub>3</sub>|| 4.27 ||-|| 7.53|| 7.88
|-
| PaF<sub>4</sub>|| Dark brown|| [[Monoclinic]]|| 12.7|| 10.7|| 8.42|| –
|-
| PaF<sub>5</sub>|| Black|| [[Tetragonal]], β-UF<sub>5</sub>|| 11.53 ||-|| 5.19|| –
|-
| ThF<sub>4</sub>|| Colorless|| Monoclinic|| 13|| 10.99|| 8.58|| 5.71
|-
| UF<sub>3</sub>|| Reddish-purple|| Hexagonal|| 7.18 ||-|| 7.34|| 8.54
|-
| UF<sub>4</sub>|| Green|| Monoclinic|| 11.27|| 10.75|| 8.40|| 6.72
|-
| α-UF<sub>5</sub>|| Bluish|| Tetragonal|| 6.52 ||-|| 4.47|| 5.81
|-
| β-UF<sub>5</sub>|| Bluish|| Tetragonal|| 11.47 ||-|| 5.20|| 6.45
|-
| UF<sub>6</sub>|| Yellowish|| Orthorhombic|| 9.92|| 8.95|| 5.19|| 5.06
|-
| NpF<sub>3</sub>|| Black or purple|| Hexagonal|| 7.129 ||-|| 7.288|| 9.12
|-
| NpF<sub>4</sub>|| Light green|| Monoclinic|| 12.67|| 10.62|| 8.41|| 6.8
|-
| NpF<sub>6</sub>|| Orange|| Orthorhombic|| 9.91|| 8.97|| 5.21|| 5
|-
| PuF<sub>3</sub>|| Violet-blue|| Trigonal|| 7.09 ||-|| 7.25|| 9.32
|-
| PuF<sub>4</sub>|| Pale brown|| Monoclinic|| 12.59|| 10.57|| 8.28|| 6.96
|-
| PuF<sub>6</sub>|| Red-brown|| Orthorhombic|| 9.95|| 9.02|| 3.26|| 4.86
|-
| AmF<sub>3</sub>|| Pink or light beige|| [[Hexagonal crystal system|hexagonal]], LaF<sub>3</sub>|| 7.04<ref name="katz">{{cite book|author = F. Weigel|title = The Chemistry of the Actinide Elements|place=Moscow|publisher = Mir| year = 1997|volume = 2|isbn = 978-5-03-001885-0|author2 = J. Katz|author3 = G. Seaborg}}</ref><ref>{{cite journal|last1=Nave|first1=S.|last2=Haire|first2=R.|last3=Huray|first3=Paul|title=Magnetic properties of actinide elements having the 5f<sup>6</sup> and 5f<sup>7</sup> electronic configurations|journal=Physical Review B|volume=28|issue=5|pages=2317–2327|year=1983|doi=10.1103/PhysRevB.28.2317|bibcode = 1983PhRvB..28.2317N }}</ref>||-|| 7.255|| 9.53
|-
| AmF<sub>4</sub>|| Orange-red|| [[Monoclinic]]|| 12.53|| 10.51|| 8.20|| –
|-
| CmF<sub>3</sub>|| From brown to white|| Hexagonal|| 4.041 ||-|| 7.179|| 9.7
|-
| CmF<sub>4</sub>|| Yellow|| Monoclinic, UF<sub>4</sub>|| 12.51|| 10.51|| 8.20|| –
|-
| BkF<sub>3</sub>|| Yellow-green|| [[Trigonal]], LaF<sub>3</sub><br /> [[Orthorhombic]], YF<sub>3</sub>|| 6.97<br /> 6.7|| -<br /> 7.09|| 7.14<br /> 4.41|| 10.15<br /> 9.7
|-
| BkF<sub>4</sub>||-|| Monoclinic, UF<sub>4</sub>|| 12.47|| 10.58|| 8.17|| –
|-
| CfF<sub>3</sub>|| -<br /> -|| Trigonal, LaF<sub>3</sub><br /> Orthorhombic, YF<sub>3</sub>|| 6. 94<br /> 6.65|| -<br /> 7.04|| 7.10<br /> 4.39|| –
|-
| CfF<sub>4</sub>|| -<br /> -|| Monoclinic, UF<sub>4</sub><br /> Monoclinic, UF<sub>4</sub>|| 1.242 <br /> 1.233|| 1.047<br /> 1.040|| 8.126<br /> 8.113|| –
|}

[[File:Einsteinium triiodide by transmitted light.jpg|thumb|left|[[Einsteinium triiodide]] glowing in the dark]]
Actinides easily react with halogens forming salts with the formulas MX<sub>3</sub> and MX<sub>4</sub> (X = [[halogen]]). So the first berkelium compound, [[Berkelium(III) chloride|BkCl<sub>3</sub>]], was synthesized in 1962 with an amount of 3 nanograms. Like the halogens of rare earth elements, actinide [[chloride]]s, [[bromide]]s, and [[iodide]]s are water-soluble, and [[fluoride]]s are insoluble. Uranium easily yields a colorless hexafluoride, which [[Sublimation (phase transition)|sublimates]] at a temperature of 56.5&nbsp;°C; because of its volatility, it is used in the separation of uranium isotopes with [[gas centrifuge]] or [[gaseous diffusion]]. Actinide hexafluorides have properties close to [[anhydride]]s. They are very sensitive to moisture and hydrolyze forming AnO<sub>2</sub>F<sub>2</sub>.<ref name=g1269>Greenwood, p.1269</ref> The [[Uranium pentachloride|pentachloride]] and black [[Uranium hexachloride|hexachloride]] of uranium were synthesized, but they are both unstable.<ref name=g222 />

Action of acids on actinides yields salts, and if the acids are non-oxidizing then the actinide in the salt is in low-valence state:
: U + 2 [[Sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] → [[Uranium(IV) sulfate|U(SO<sub>4</sub>)<sub>2</sub>]] + 2 H<sub>2</sub>
: 2 Pu + 6 [[Hydrochloric acid|HCl]] → 2 [[Plutonium(III) chloride|PuCl<sub>3</sub>]] + 3 H<sub>2</sub>
However, in these reactions the regenerating hydrogen can react with the metal, forming the corresponding hydride. Uranium reacts with acids and water much more easily than thorium.<ref name=g222 />

Actinide salts can also be obtained by dissolving the corresponding hydroxides in acids. Nitrates, chlorides, sulfates and perchlorates of actinides are water-soluble. When crystallizing from aqueous solutions, these salts form hydrates, such as [[Thorium(IV) nitrate|Th(NO<sub>3</sub>)<sub>4</sub>·6H<sub>2</sub>O]], [[Thorium(IV) sulfate|Th(SO<sub>4</sub>)<sub>2</sub>·9H<sub>2</sub>O]] and [[Plutonium(III) sulfate|Pu<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·7H<sub>2</sub>O]]. Salts of high-valence actinides easily hydrolyze. So, colorless sulfate, chloride, perchlorate and nitrate of thorium transform into basic salts with formulas Th(OH)<sub>2</sub>SO<sub>4</sub> and Th(OH)<sub>3</sub>NO<sub>3</sub>. The solubility and insolubility of trivalent and tetravalent actinides is like that of lanthanide salts. So [[phosphate]]s, [[fluoride]]s, [[oxalate]]s, [[iodate]]s and [[carbonate]]s of actinides are weakly soluble in water; they precipitate as hydrates, such as [[Thorium(IV) fluoride|ThF<sub>4</sub>·3H<sub>2</sub>O]] and [[Thorium(IV) chromate|Th(CrO<sub>4</sub>)<sub>2</sub>·3H<sub>2</sub>O]].<ref name=g222 />

Actinides with oxidation state +6, except for the AnO<sub>2</sub><sup>2+</sup>-type cations, form [AnO<sub>4</sub>]<sup>2−</sup>, [An<sub>2</sub>O<sub>7</sub>]<sup>2−</sup> and other complex anions. For example, uranium, neptunium and plutonium form salts of the Na<sub>2</sub>UO<sub>4</sub> ([[uranate]]) and (NH<sub>4</sub>)<sub>2</sub>U<sub>2</sub>O<sub>7</sub> (diuranate) types. In comparison with lanthanides, actinides more easily form [[coordination compound]]s, and this ability increases with the actinide valence. Trivalent actinides do not form fluoride coordination compounds, whereas tetravalent thorium forms K<sub>2</sub>ThF<sub>6</sub>, KThF<sub>5</sub>, and even K<sub>5</sub>ThF<sub>9</sub> complexes. Thorium also forms the corresponding [[sulfate]]s (for example Na<sub>2</sub>SO<sub>4</sub>·Th(SO<sub>4</sub>)<sub>2</sub>·5H<sub>2</sub>O), [[nitrate]]s and [[thiocyanate]]s. Salts with the general formula An<sub>2</sub>Th(NO<sub>3</sub>)<sub>6</sub>·''n''H<sub>2</sub>O are of coordination nature, with the [[coordination number]] of thorium equal to 12. Even easier is to produce complex salts of pentavalent and hexavalent actinides. The most stable coordination compounds of actinides – tetravalent thorium and uranium – are obtained in reactions with diketones, e.g. [[acetylacetone]].<ref name=g222 />