Explain the following variations in atomic or ionic radii, by completing the following sentences: fe > fe2+ > fe3+ 1. the 4s valence electrons in fe are on average from the nucleus than the 3d electrons, so fe is larger than fe2+. 2. because there are five 3d orbitals, in fe2+ at least must contain a pair of electrons. 3. removing one more electron from fe2+ to form fe3+ significantly repulsion, increasing the nuclear charge experienced by each of the other d electrons and decreasing the size of the ion.