The complex ion [Cu(H2O)6]2+ is blue due to d-d transitions.

The common oxidation state of actinides in their compounds is +4.

Chromium commonly exhibits a +6 oxidation state in chromates (CrO4^2-).

In Cr2O7^2-, chromium has a common oxidation state of +6.

Chromium commonly exhibits a +6 oxidation state in compounds such as chromium trioxide (CrO3).

Transition metals commonly exhibit a +2 oxidation state due to the loss of two 4s electrons.

Chromium has an electron configuration of [Ar] 4s1 3d5 due to stability from half-filled d-orbitals.

The electronic configuration of Lanthanum (atomic number 57) is [Xe] 6s2.

Manganese can exhibit a maximum oxidation state of +7 in compounds like KMnO4.

In KMnO4, the oxidation state of manganese is +7.

In UF6, Uranium is in the +6 oxidation state as it forms six bonds with fluorine.

In CrO3, chromium has a primary oxidation state of +6.

The color of transition metal complexes arises from the presence of unpaired electrons and the crystal field splitting of d-orbitals.

The color of transition metal compounds arises from the presence of unpaired electrons and d-d transitions.

Thorium (Th) is used in nuclear reactors due to its ability to breed fissile uranium-233.

Iron is used as a catalyst in the Haber process for the synthesis of ammonia from nitrogen and hydrogen.

Scandium has the highest atomic radius among the given d-block elements.

Mercury (Hg) is the only metal that is liquid at room temperature.

Rutherfordium (Rf) has the highest atomic number among the given options.

Tungsten has the highest melting point among the d-block elements due to its strong metallic bonding.

Osmium has the highest melting point among the given options due to its strong metallic bonding.

Iron (Fe) is a d-block element as it has partially filled d-orbitals.

Plutonium is a member of the actinide series, which includes elements with atomic numbers 89 to 103.

Uranium (U) is a part of the actinide series, which consists of elements with atomic numbers from 89 to 103.

Zinc (Zn) is not considered a transition metal because it does not have an incomplete d-subshell in its elemental state.

Plutonium is widely used in nuclear reactors and weapons due to its fissile properties.

D-block elements typically form colored compounds due to d-d electron transitions.

F-block elements typically form colored ions due to the presence of unpaired electrons in f-orbitals.

Lanthanides are known for their high density, which is a characteristic property of these elements.

Chromium can exhibit multiple oxidation states including +2, +3, and +6.