The transition (d-block) metals share several typical properties; two are described below.
Step 1: They form complex compounds readily. Their small, highly charged cations with vacant d orbitals strongly attract lone-pair donors (ligands) such as \(NH_3\), \(CN^{-}\) and \(H_2O\), giving coordination complexes like \([Fe(CN)_6]^{4-}\) and \([Cu(NH_3)_4]^{2+}\).
Step 2: They are paramagnetic. Most transition metal atoms and ions contain unpaired electrons in their d orbitals; these unpaired electrons are attracted by a magnetic field, so the substances are paramagnetic, and the magnetic moment increases with the number of unpaired electrons following \(\mu = \sqrt{n(n+2)}\) BM.
Together with variable oxidation states, coloured ions and catalytic behaviour, these features distinguish transition metals from typical s- and p-block metals.
\[\boxed{\text{Complex formation and paramagnetism are two key traits}}\]