Copper primarily exists in the +2 valence state (Cu²⁺), exhibiting characteristic coordination structures, such as octahedral or planar square configurations distorted by the Jameer-Taylor effect; the +1 valence state (Cu⁺) mostly exists in tetrahedral coordination. Cu²⁺ salts are typically blue or green due to d-d electron transitions, while most Cu⁺ salts are colorless. Most common copper salts are readily soluble in water.

Cu²⁺ reacts with alkalis to form a blue flocculent precipitate Cu(OH)₂, which is soluble in ammonia to form a deep blue complex ion [Cu(NH₃)₄]²⁺. Copper ions can undergo displacement reactions with active metals (such as iron and zinc), being reduced to elemental copper. Cu²⁺ has some oxidizing properties and can be reduced by reducing agents such as iodide ions (I⁻) and aldehydes. Copper salts have poor thermal stability and readily decompose upon heating to form black copper oxide (CuO). It is widely used in electroplating solutions, agricultural fungicides (such as Bordeaux mixture), catalysts, analytical chemical reagents, and blue or green pigments.

Copper powder possesses a face-centered cubic crystal structure, characterized by its high specific surface area and diverse morphologies (such as spherical and flake-like shapes), significantly enhancing its reactivity compared to bulk copper. It typically exhibits a characteristic purplish-red color and excellent electrical conductivity; however, when the particle size reaches the nanoscale, it can appear black. Copper powder exhibits strong reducing properties, readily reacting with oxygen to form copper oxide (CuO) under heating conditions. Prolonged exposure to humid air gradually forms basic copper carbonate, i.e., verdigris (Cu₂(OH)₂CO₃). It is soluble in oxidizing acids such as concentrated sulfuric acid and nitric acid. Furthermore, copper powder can displace noble metal ions in solution, such as Ag⁺, demonstrating excellent reducing ability. Due to its unique physicochemical properties, copper powder is widely used in powder metallurgy, conductive fillers (such as conductive inks and adhesives), high-efficiency catalysts, lubricating additives, and colorants in fireworks products.