Nickel

• NICKEL (Ni2+) is a hard, silvery-white metal, it is ductile, malleable and very strong.
• It melts at 1455°C, and is slightly magnetic.
• HCl (both dilute and concentrated) and dilute H2SO4 dissolve nickel with the formation of hydrogen gas.
• concentrated, hot H2SO4 dissolves nickel with the formation of sulfur dioxide (SO2) gas.
• Cold, dilute and concentrated HNO3 dissolve nickel readily with the evolution of nitrogen dioxide (NO2) gas.
• The stable nickel (II) salts are derived from nickel (II) oxide, NiO, which is a green substance.
• The dissolved nickel (II) salts are green, owing to the color of the hexaquonickelate (II) ion complex [Ni(H2O)6]2+; or simply the Nickel (II) ion.
• A brownish-black nickel (III) oxide Ni2O3 also exists, but this dissolves in acids forming nickel (II) ions.
• With dilute HCl this reaction yields chlorine gas.
• While nickel forms two series of compounds, only those in which it has a

  valence of two (+2) are important. Compounds of nickel generally have a bright green color which they impart to their solutions.