D-block Transition Metals

Elements of the d-block have their outer electrons found where?

In d-orbitals.

What is a transition metal?

An element that possesses a partially filled d sub-shell as an atom or in its stable ions.

Are all d block elements classed as transition metals?

No- Scandium and Zinc are not classed as transition metals, even though they are found in the d block.

Why is zinc not classed as a transition metal?

The Zn atom and the Zn²⁺ ion have full d-orbitals; it cannot be classed as a transition metal as transition metals have a partially filled d sub-shell.

Why is scandium not classed as a transition metal?

Sc has an empty d sub-shell; the d sub-shell is not partially filled so it cannot be classed as a transition metal.

Which orbital fills first, 3d or 4s?

The 4s orbital fills first as it has a lower energy than 3d; it also loses its electrons first.

Copper and Chromium are 2 exceptions to remember when writing electronic configuration. Why?

Both only have 1 electron in the 4s orbital, with chromium having a half-filled d subshell and copper a complete d subshell.

There is extra stability associated with having a half-filled d subshell or a completely filled d subshell.

Chromium: [Ar] 3d⁵ 4s¹

Copper: [Ar] 3d¹⁰ 4s¹

What are some key characteristics of transition metals?

• They have variable oxidation states.

• They form complex ions, which are coloured.

• Can act as catalysts.

Why can transition metals exhibit variable oxidation states?

The energies of the 4s and 3d orbitals are very similar, so the energy required to remove any of the electrons found in these orbitals (ionisation energy) is similar.

Multiple electrons can be removed without big jumps in ionisation energies.

State the common oxidation states of some transition metals.

Chromium: +3 and +6

Manganese: +2, +4, and +7

Iron: +2 and +3

Copper: +1 and +2