  We perform calculations of the energy shift of the nuclear clock transition
frequency $^{229}$Th as a function of the number of electrons in Th ion.
  We demonstrate that the dependence of the nuclear frequency on electron
configuration is significant. E.g., removing one electron from the atom leads
to relative shift of the nuclear frequency $\sim 10^{-7}$, which is twelve
orders of magnitude larger than expected relative uncertainty of the nuclear
clock transition frequency ($\sim 10^{-19}$). This leads to difference of the
nuclear clock frequencies in Th~IV, Th~III, Th~II and Th~I.
  The relative change of the nuclear frequency between neutral Th and its bare
nucleus is 1\%. We also calculate the field shift constants for isotopic and
isomeric shifts of atomic electron transitions in Th ions.
