Where the d-block sits and how its electrons are arranged. The trends in size, ionisation enthalpy and oxidation states, and why these elements form coloured, magnetic ions.
3 lessons, about 1 h 50 min4 simulations11 problems5 practice questionsPython in every lesson
Created by StemPy LabIron, copper and gold sit in the middle of the periodic table, in the block where the d orbitals fill. A transition element has an incomplete d subshell in its atom or in a common ion, so zinc does not qualify. Chromium and copper break the filling pattern, and every ion of the first series loses its 4s electrons before its 3d electrons.
Across the first series the nuclear charge rises by one at each step, but the new electron goes into an inner subshell and shields the outer 4s electrons well. So size, ionisation enthalpy and density change slowly. Melting points peak in the middle, where many d electrons bond the atoms, and the electrode potentials show why copper is the odd one out.
A copper sulphate solution is blue, an iron nail rusts to a brown solid, and a vanadium compound can be violet, green, blue or yellow. The 4s and 3d electrons have close energies, so a transition element can give up different numbers of them. Ions with unpaired d electrons are magnetic, and ions with a partly filled d subshell absorb visible light.
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