d and f-Block Elements Test - 6

The elements in the group 11, of the modern periodic table, consisting of copper, silver, and gold are referred to as coinage metals. Roentgenium placed in this group in the periodic table, although it is yet to be confirmed that it behaves like the heavier homologue to gold.

Coinage metals are usually alloys designed to resist corrosion and wear during a thirty to forty year lifespan. Aluminum, nickel, copper, bronze, gold, tin, and silver are some of the metals that have been used for this purpose.

Platinum, however is not a coinage metal.

All the elements of the lanthanide series resemble each other very closely due to the similarity in the configuration of the outermost and the penultimate shells. They are also called rare earth elements. 4f and 5f belong to different energy levels. Hence, shielding effects in them are not the same. Shielding of 4f is more than that of 5f.

The electronic configuration of Cr is (3d)⁵ (4s)¹. Thus, it will have +6 as its highest oxidation state.

In this state, chromium is neither oxidising nor reducing and is believed to be its most stable state.
This is because in +3 oxidation state, chromium has the stable configuration of half-filled t₂g orbitals [t₂g³ e_g⁰].

Transition metal compounds are usually coloured. This is due to the electronic transitions within d-orbitals.

In transition series, colour appears due to d-d transition in the visible region. Cr³⁺ has d³ configuration. So, d-d transition is possible. Hence, the compound will be coloured.

The electronic configuration of Mn²⁺ (25) is 3d⁵ 4s⁰.
This is a stable configuration of half-filled d-orbitals.