Iron corrodes in oxygen-free water.

Iron corrodes more rapidly in salt water because its electrochemical potential is higher.

Corrosion of iron can be minimized by forming a contact with another metal with a higher reduction potential.

Corrosion of iron can be minimized by forming an impermeable barrier at its surface.

[Co(NH₃)₆]Cl₃

[Pt(NH₃)₂Cl₂]

[Co(NH₃)₄Cl₂]

[Co(NH₃)₅Cl]Cl₂

Cr³⁺   and   Co³⁺

Co³⁺    and    Cr³⁺

Co³⁺    and    Co³⁺

Cr³⁺    and    Cr³⁺

S₂ is paramagnetic like oxygen.

Rhombic and monoclinic sulphur have S₈ molecules.

S₈ ring has a crown shape.

The S-S-S bond angles in the S₈ and S₆ rings are the same.