The oxides and hydroxides of yttrium are yttrium oxide (Y₂O₃) and yttrium hydroxide (Y(OH)₃), respectively, and they are both white solids which are hardly soluble in water. Among them, yttrium oxide can be prepared by heating yttrium carbonate or yttrium oxalate. Alternatively the oxychloride, Y₃O₄Cl can be heated in air to yield the oxide.

Yttrium hydroxide can be precipitated by the reaction of soluble yttrium compounds with sodium hydroxide or ammonia, and can also be obtained by the hydrolysis of yttrium alkoxide. Hydroxy acids and sugars present in the solution will prevent the formation of precipitates due to the formation of stable coordination compounds. Yttrium hydroxide can be decomposed by heating. Firstly, basic yttrium oxide (YO(OH)) is formed, and when heating is continued yttrium oxide is obtained. Both yttrium oxide and yttrium hydroxide are easily soluble in strong acids to form corresponding yttrium salts.

Yttrium chalcogenides Y₂S₃, Y₂Se₃, and Y₂Te₃ are known. They can be obtained by the direct combination of elementary substances or anhydrous chlorine. The reaction of compounds with chalcogenide gives: [9]

Y₂O₃ + 3 H₂E → Y₂E₃ + 3 H₂O

2 Y + 3 E → Y₂E₃ (E = S, Se, Te)

Yttrium halides can be obtained by reacting yttrium oxide, yttrium hydroxide or yttrium carbonate with the corresponding hydrohalic acid solution. For yttrium chloride (YCl₃) and yttrium bromide (YBr₃), the yttrium halide hydrate can be precipitated by cooling their saturated solution or by passing in the corresponding hydrogen halide. Yttrium halides, like lanthanide metal halides, cannot be obtained by direct heating of the hydrate, otherwise yttrium oxyhalide (YOX) will be formed. Anhydous compounds can be obtained by heating the hydrate in a hydrogen halide stream, or by treating it with ammonium halide and sulfoxide. [10] In addition to forming hydrates (YF₃ · 1 / 2H₂O, YCl₃ · 6H₂O, YBr₃·6H₂O, and YI₃·8H₂O), yttrium halides can also form complexes with some ligands. Substances, such as [Y(Me₃PO)₆]X₃ or [Y(Me₃AsO)₆]X₃ (X = Cl, Br, I) and the like with phosphine oxides. [11] Yttrium and halogens (except fluorine [12] ) or pseudohalogens can also form complexes, such as Cs₃[Y₂I₉], (Bu₄N)₃ [Y(NCS)₆ ], etc.^[1]

The reaction of yttrium metal with yttrium chloride or yttrium bromide yields low-oxidation monohalides YX and yttrium sesquichloride Y₂Cl₃, and sesquibromide Y₂Br₃ (X = Cl, Br).^[2]

Two yttrium hydrides are known at standard conditions, YH₂ and YH₃.^[3] YH₉, a polyhydride is stable at high pressures, and is a superconductor at temperatures up to 243K.^[4][5]

Yttrium and pnictides can form compounds with the chemical formula YE (E = N, P, As, Sb). They can be hydrolyzed in humid air and emit volatile hydrides EH₃.

Yttrium and carbon can form a variety of compounds, such as Y₂C₃,^[6] YC₂.^[7] They can be made in several ways:

2 Y + 3 C → Y₂C₃

Y₂O₃ + 7 C → 2 YC₂ + 3 CO ↑

There are also several yttrium silicides, such as YSi₂,^[8] Y₅Si₄ and YSi.^[9]

Yttrium and boron can also form many colourful compounds, such as gold YB₄ , blue YB₆ , light blue YB₁₂. They are metallic; YB₆₆ is a semiconductor, and the resistivity at room temperature is 10⁶ Ω·cm.^[10]

Most of the salts from strong acids are soluble in water. The ionic radius (0.900) of yttrium in [Y(H₂O)₆]³⁺ is similar to that of holmium [Ho(H₂O)₆]³⁺ (0.901), and differs from easily hydrolyzed [Sc(H₂O)₆]³⁺.^[11]

Yttrium carbonate and yttrium oxalate are sparingly soluble in water, but are dissolved in acid. They decompose on heating to yttrium oxide.

Organic acid salts of yttrium include yttrium formate, yttrium acetate, yttrium propionate, yttrium butyrate. They are all made by dissolving the carbonate or oxide in the corresponding acid. Aromatic polycarboxylates like phthalic acid or trimellitic acid have a rigid shape, and can coordinate more than one yttrium atom to form a metal-organic framework compound.^[12][13]

• Category:Yttrium minerals