Physical properties: Light yellow crystal, commonly known as sulfur, is insoluble in water and has a higher density than water. When added to water, it forms a white suspension, slightly soluble in alcohol, and easily soluble in CS2 (for washing sulfur attached to the test tube wall, CS2 can be used to dissolve it)

Chemical properties

Chemical properties: The valence of elemental S is 0, not the highest valence+6 or the lowest valence -2, and it is in an intermediate valence state. Therefore, elemental sulfur has both oxidizing and reducing properties.

① Reacts with most metals under heating conditions to form divalent sulfides, at which point sulfur exhibits oxidizing properties. Cu2S and FeS are both low-priced sulfides of metals. Sulfur has weak oxidizing properties and can only oxidize metals to lower valence states. CuS is obtained through other methods.

S+2Na=Na₂S (white) Heating oxidation

S+Fe=FeS (black) heating

S+2Cu=Cu₂S (black) heating

② Under the conditions of ignition or heating in reaction with non-metallic materials

S+O₂=SO₂ ignition reducibility

S+H₂=H₂S Heating Oxidation

③ It exhibits both oxidizing and reducing properties. Under heating conditions, sulfur can react with strong alkaline solutions. According to this reaction principle, residual sulfur on the inner wall of the glass instrument can be removed using NaOH solution under heating conditions

Heat: 6NaOH+3S=△=2NNa₂S+Na₂SO₃+3H₂O

When there is a high amount of sulfur, Na₂S+S=△=Na₂S₂

Na₂S+2S=△=Na₂S₃ (more)

Na₂S+3S=△=Na₂S₄ (more)

Na₂S+4S=△=Na₂S₅ (excess)

And: Na₂SO₃+S=△=Na₂S₂O₃ (sodium thiosulfate), its solution will change from yellow to orange red due to the continuous increase of Na₂Sx and x

S can also react with concentrated sulfuric acid and concentrated nitric acid under heating conditions:

S+2H₂SO₄ (concentrated)=△=3SO₂ ↑+2H₂O

6HNO₃ (concentrated)+S=△=6NO₂ ↑+H₂SO4+2H₂O

4HNO₃ (dilute)+3S==3SO₂ ↑+2H₂O+4NO ↑