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Transition metals exhibit characteristic physical properties arising from metallic bonding involving both s and d electrons.

Atomic radii decrease slightly across the 3d series due to poor shielding by d-electrons, then increase at Zn. The variation (~10 pm from Ti to Cu) is much smaller than in s or p-blocks, enabling alloy formation between similar-sized atoms.

Melting points are high, peaking at Cr (1907 degrees C) in the 3d series and W (3422 degrees C) overall. Mn is anomalous (1246 degrees C) due to its complex crystal structure. Zn has the lowest 3d m.p. (420 degrees C) because d^10 electrons contribute little to bonding.

Ionisation enthalpies generally increase across the series with irregularities at d^5 (Mn) and d^10 (Zn) due to extra stability. The sum IE1 + IE2 determines +2 state formation ease.

Standard electrode potentials generally become less negative (more positive) across the series. Cu is unique: E degree(Cu^2+/Cu) = +0.34 V (positive), meaning Cu doesn't dissolve in non-oxidising acids. Mn shows an anomalous dip (more negative than expected) due to the high stability of Mn^2+ (d^5).

Colour arises from d-d transitions in partially filled d-orbitals. d^0 and d^10 ions are colourless. d^5 high spin (Mn^2+) gives very faint colour because all transitions are spin-forbidden.