  We consider the problem of electron energy states related to strongly
localized potential of a single impurity in graphene. Our model simulates the
effect of impurity atom substituting the atom of carbon, on the energy spectrum
of electrons near the Dirac point. We take into account the internal spin-orbit
interaction, which can modify the structure of electron bands at very small
neighborhood of the Dirac point, leading to the energy gap. This makes possible
the occurrence of additional impurity states in the vicinity of the gap.
