:Protactinium(IV) oxide

{{Chembox

| IUPACName = Protactinium(IV) oxide

|Section1={{Chembox Identifiers

| CASNo = 12036-03-2

| SMILES = O=[Pa]=O

| StdInChI = 1S/2O.Pa

| StdInChI_Ref = {{stdinchicite|correct|??}}

| StdInChIKey = FUMADFKVOBAYPE-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|correct|??}}}}

|Section2={{Chembox Properties

| O=2 | Pa=1

| MeltingPtC = 2927

| MeltingPt_ref =

| Appearance = Black crystals}}

| Section3 = {{Chembox Structure

| CrystalStruct = Fluorite (cubic), cF12

| SpaceGroup = Fm3m, No. 225

| LattConst_a = 544.6 pm{{cite journal |author1=Christine Guéneau |author2=Alain Chartier |author3=Paul Fossati |author4=Laurent Van Brutzel |author5=Philippe Martin |title=Thermodynamic and Thermophysical Properties of the Actinide Oxides |journal=Comprehensive Nuclear Materials 2nd Ed. |date=2020 |volume=7 |pages=111–154 |doi=10.1016/B978-0-12-803581-8.11786-2 |isbn=9780081028667 |s2cid=261051636 |language=en}}

}}

|Section7={{Chembox Hazards

| NFPA-H = 4

| NFPA-F =

| NFPA-R =

| NFPA-S = RA

}}

|Section8 = {{Chembox Related

|OtherAnions =

|OtherCations = Thorium(IV) oxide
Uranium(IV) oxide

| OtherCompounds =

}}

}}

Protactinium(IV) oxide is a chemical compound with the formula PaO₂. The black oxide is formed by reducing Pa₂O₅ with hydrogen at 1 550 °C. Protactinium(IV) oxide does not dissolve in H₂SO₄, HNO₃, or HCl solutions, but reacts with HF.{{cite journal | doi = 10.1021/ja01652a011 | year = 1954 | last1 = Sellers | first1 = Philip A. | last2 = Fried | first2 = Sherman | last3 = Elson | first3 = Robert E. | last4 = Zachariasen | first4 = W. H. | journal = Journal of the American Chemical Society | volume = 76 | pages = 5935 | title = The Preparation of Some Protactinium Compounds and the Metal | issue = 23| url = https://digital.library.unt.edu/ark:/67531/metadc172625/ }}Boris F. Myasoedov, H. W. Kirby, & Ivan G. Tananaev (2006) Protactinium, Chapter 4 in Morss, Lester R. & Edelstein, Norman M. & Fuger, Jean, (edit.) [http://radchem.nevada.edu/classes/rdch710/files/Protactinium.pdf The Chemistry of the Actinide and Transactinide Elements] {{Webarchive|url=https://web.archive.org/web/20170826210935/http://radchem.nevada.edu/classes/rdch710/files/Protactinium.pdf |date=2017-08-26 }} (PDF) (3. painos). Dordrecht: Springer. ss. 161–252.{{rp|195}}

As protactinium(IV) oxide, like other protactinium compounds, is radioactive, toxic and very rare, it has no known technological use.