Transition Metals
Groups 3 to 12: the d-block metals, from scandium to copernicium, where the inner d subshell fills.
What they have in common
Moving across the d-block, electrons go into the (n−1)d subshell while the outer ns shell stays at one or two electrons. Because those d and s energies are close, transition metals can lose different numbers of electrons, which is why iron forms both Fe²⁺ and Fe³⁺ and manganese reaches +7 in permanganate.
Partly filled d subshells also explain their coloured compounds, magnetic behaviour (iron, cobalt, nickel) and usefulness as catalysts. Chromium and copper are the classic configuration exceptions: they take a 4s electron into 3d to reach a half-filled (3d⁵) or filled (3d¹⁰) subshell.
- Variable oxidation states
- Coloured ions and compounds
- High melting points and densities (tungsten melts at 3695 K)
- Good electrical and thermal conductors
- Important catalysts (Fe in the Haber process, Pt and Pd in catalytic converters)
Transition metals at a glance
| Element | Z | Mass | Configuration | Valence e⁻ | Charges | EN | Radius (pm) |
|---|---|---|---|---|---|---|---|
| Scandium (Sc) | 21 | 44.956 | [Ar] 3d1 4s2 | 3 | 3+ | 1.36 | 144 |
| Titanium (Ti) | 22 | 47.867 | [Ar] 3d2 4s2 | 4 | 4+, 3+ | 1.54 | 136 |
| Vanadium (V) | 23 | 50.941 | [Ar] 3d3 4s2 | 5 | 5+, 3+ | 1.63 | 125 |
| Chromium (Cr) | 24 | 51.996 | [Ar] 3d5 4s1 | 6 | 3+, 6+ | 1.66 | 127 |
| Manganese (Mn) | 25 | 54.938 | [Ar] 3d5 4s2 | 7 | 2+, 4+, 7+ | 1.55 | 139 |
| Iron (Fe) | 26 | 55.845 | [Ar] 3d6 4s2 | 8 | 2+, 3+ | 1.83 | 125 |
| Cobalt (Co) | 27 | 58.933 | [Ar] 3d7 4s2 | 9 | 2+, 3+ | 1.88 | 126 |
| Nickel (Ni) | 28 | 58.693 | [Ar] 3d8 4s2 | 10 | 2+ | 1.91 | 121 |
| Copper (Cu) | 29 | 63.546 | [Ar] 3d10 4s1 | 11 | +, 2+ | 1.9 | 138 |
| Zinc (Zn) | 30 | 65.38 | [Ar] 3d10 4s2 | 12 | 2+ | 1.65 | 131 |
| Yttrium (Y) | 39 | 88.906 | [Kr] 4d1 5s2 | 3 | 3+ | 1.22 | 162 |
| Zirconium (Zr) | 40 | 91.224 | [Kr] 4d2 5s2 | 4 | 4+ | 1.33 | 148 |
| Niobium (Nb) | 41 | 92.906 | [Kr] 4d4 5s1 | 5 | 5+ | 1.6 | 137 |
| Molybdenum (Mo) | 42 | 95.96 | [Kr] 4d5 5s1 | 6 | 6+ | 2.16 | 145 |
| Technetium (Tc) | 43 | [98] | [Kr] 4d5 5s2 | 7 | 7+ | 1.9 | 156 |
| Ruthenium (Ru) | 44 | 101.07 | [Kr] 4d7 5s1 | 8 | 3+ | 2.2 | 126 |
| Rhodium (Rh) | 45 | 102.906 | [Kr] 4d8 5s1 | 9 | 3+ | 2.28 | 135 |
| Palladium (Pd) | 46 | 106.42 | [Kr] 4d10 | 12 | 2+ | 2.2 | 131 |
| Silver (Ag) | 47 | 107.868 | [Kr] 4d10 5s1 | 11 | + | 1.93 | 153 |
| Cadmium (Cd) | 48 | 112.411 | [Kr] 4d10 5s2 | 12 | 2+ | 1.69 | 148 |
| Hafnium (Hf) | 72 | 178.49 | [Xe] 4f14 5d2 6s2 | 4 | 4+ | 1.3 | 150 |
| Tantalum (Ta) | 73 | 180.948 | [Xe] 4f14 5d3 6s2 | 5 | 5+ | 1.5 | 138 |
| Tungsten (W) | 74 | 183.84 | [Xe] 4f14 5d4 6s2 | 6 | 6+ | 2.36 | 146 |
| Rhenium (Re) | 75 | 186.207 | [Xe] 4f14 5d5 6s2 | 7 | 7+ | 1.9 | 159 |
| Osmium (Os) | 76 | 190.23 | [Xe] 4f14 5d6 6s2 | 8 | 4+ | 2.2 | 128 |
| Iridium (Ir) | 77 | 192.217 | [Xe] 4f14 5d7 6s2 | 9 | 4+ | 2.2 | 137 |
| Platinum (Pt) | 78 | 195.084 | [Xe] 4f14 5d9 6s1 | 10 | 2+, 4+ | 2.28 | 128 |
| Gold (Au) | 79 | 196.967 | [Xe] 4f14 5d10 6s1 | 11 | +, 3+ | 2.54 | 144 |
| Mercury (Hg) | 80 | 200.59 | [Xe] 4f14 5d10 6s2 | 12 | +, 2+ | 2 | 149 |
| Rutherfordium (Rf) | 104 | [267] | [Rn] 5f14 6d2 7s2 | 4 | — | — | — |
| Dubnium (Db) | 105 | [268] | [Rn] 5f14 6d3 7s2 | 5 | — | — | — |
| Seaborgium (Sg) | 106 | [271] | [Rn] 5f14 6d4 7s2 | 6 | — | — | — |
| Bohrium (Bh) | 107 | [272] | [Rn] 5f14 6d5 7s2 | 7 | — | — | — |
| Hassium (Hs) | 108 | [270] | [Rn] 5f14 6d6 7s2 | 8 | — | — | — |
| Meitnerium (Mt) | 109 | [276] | [Rn] 5f14 6d7 7s2 | 9 | — | — | — |
| Darmstadtium (Ds) | 110 | [281] | [Rn] 5f14 6d9 7s1 | 10 | — | — | — |
| Roentgenium (Rg) | 111 | [280] | [Rn] 5f14 6d10 7s1 | 11 | — | — | — |
| Copernicium (Cn) | 112 | [285] | [Rn] 5f14 6d10 7s2 | 12 | — | — | — |
Questions students ask
Why do transition metals have multiple charges?
Their ns and (n−1)d electrons have similar energies, so different numbers can be removed.
Are zinc, cadmium and mercury transition metals?
They sit in the d-block (group 12), so many tables include them, but their d subshell is always full. Strict IUPAC wording defines a transition element as one with an incomplete d subshell in the atom or a common ion, which excludes group 12.
Why are transition metal compounds coloured?
In a compound, the d orbitals split into levels a small energy gap apart. Electrons absorb visible light to jump that gap, and we see the complementary colour.