* Shape: The central silicon atom has six fluorine atoms surrounding it, forming an octahedral shape. This shape is symmetrical.

* Electronegativity: Fluorine is much more electronegative than silicon. This means each fluorine atom pulls electron density towards itself, creating a dipole moment within each Si-F bond. However, because of the symmetrical octahedral shape, these individual dipole moments cancel each other out.

* Net Dipole Moment: Since the individual dipole moments cancel, the molecule as a whole has a net dipole moment of zero.

Therefore, SiF6 2- is nonpolar.