All the elements in Group 17 are gases.

The Group 13 elements are all metals.

Elements of Group 16 have lower ionization enthalpy values compared to those of Group 15 in the corresponding periods.

For Group 15 elements, the stability of + 5 oxidation state increases down the group.

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⁺