  We apply the perturbative chiral quark model (PCQM) at one loop to analyse
the electromagnetic structure of nucleons. This model is based on an effective
Lagrangian, where baryons are described by relativistic valence quarks and a
perturbative cloud of Goldstone bosons. Including the electromagnetic
interaction we first develop the formalism up to one-loop in the Goldstone
boson fluctuation relying on renormalization by use of counterterms. Local
gauge invariance is satisfied both on the Lagrangian level and also for the
relevant baryon matrix elements in the Breit frame. We apply the formalism to
obtain analytical expressions for the nucleon charge and magnetic form factors,
which are expressed in terms of fundamental parameters of low-energy
pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong
pion-nucleon form factor) and of only one model parameter (radius of the
nucleonic three-quark core). A detailed numerical analysis for the nucleon
magnetic moments, charge and magnetic radii and also for the momentum
dependence of form factors is presented.
