Question

Maximum oxidation state of chromium is:

Answer 1

Hint: The maximum oxidation state of chromium is equal to the number of valence electrons present in the neutral atom. The maximum oxidation state of chromium is equal to its group number.

Complete answer:
In the modern periodic table, the chromium metal is present in the group 6. It is a transition metal and belongs to the first transition series. The atomic number of chromium is 24. Its electronic configuration is \[\left[ {{\rm{Ar}}} \right]{\rm{3}}{{\rm{d}}^5}{\rm{4}}{{\rm{s}}^1}{\rm{ }}\] . It has five electrons in 3d subshell and one electron in 4s subshell. Thus, chromium metal has six valence electrons. Chromium can lose some or all of its valence electrons to form ions with different oxidation states. Thus chromium shows the oxidation states of +1, +2, +3, +4, +5 and +6 respectively.
The most common oxidation states of chromium are +2, +3 and +6.
Maximum oxidation state of chromium is +6. It is obtained when five 3d electrons and one 4s electron are removed. Thus, when all the valence electrons of chromium are lost, the maximum oxidation state of +6 is obtained.
The compounds showing maximum oxidation state of chromium are potassium dichromate, chromium trioxide and chromic acid.

Note: Since chromium shows variable oxidation states, potassium dichromate can act as a strong oxidizing agent. During the reaction, potassium dichromate itself undergoes reduction. During reduction of potassium dichromate, the oxidation number of chromium decreases. Due to the property of variable oxidation states, chromium also acts as a catalyst. Chromium forms alloys with metals such as iron, nickel and cobalt.