Explain the following variations in atomic or ionic radii:

Fe>Fe2+>Fe3+

1. The 4s valence electrons in Fe are on average [ Select ] ["closer", "farther"] from the nucleus than the 3d electrons, so Fe is larger than Fe2+.

2. Because there are five 3d orbitals, in Fe2+ at least [ Select ] ["three orbitals", "two orbitals", "five orbitals", "four orbitals", "one orbital"] must contain a pair of electrons.

3. Removing one more electron from Fe2+ to form Fe3+ significantly [ Select ] ["reduces", "increases"] repulsion, increasing the nuclear charge experienced by each of the other d electrons and decreasing the size of the ion.