According to the NCERT text and Table 4.2, the standard electrode potential values ($E^{\ominus}_{M^{2+}/M}$) for the given elements are:

1. Fe (Z=26): $-0.44 \text{ V}$
2. Co (Z=27): $-0.28 \text{ V}$
3. Ni (Z=28): $-0.25 \text{ V}$
4. Cu (Z=29): $+0.34 \text{ V}$

Copper (Cu) is the only metal in the first transition series (3d series) that has a positive standard electrode potential ($+0.34 \text{ V}$). This unique behavior indicates that copper is unable to liberate hydrogen from acids. The positive value arises because the high energy required to transform $Cu(s)$ to $Cu^{2+}(aq)$ (sum of high enthalpy of atomisation and ionisation) is not balanced by its hydration enthalpy .