Iodine heptafluoride

<p>Iodine heptafluoride is an <a href="/facts/Interhalogen_compound/TBED2c9B">interhalogen compound</a> with the chemical formula <a href="/facts/Iodine/JlfMecMf">I</a><a href="/facts/Fluoride/LpqNMzwa">F</a>7.  It has an unusual <a href="/facts/Pentagonal_bipyramid_molecular_geometry/tQ4fA46l">pentagonal bipyramidal</a> structure, with <a href="/facts/Hermann%25E2%2580%2593Mauguin_notation/NGHDFXKC">D5h symmetry</a>, as predicted by <a href="/facts/VSEPR_theory/WqsRgVRV">VSEPR theory</a>. The molecule can undergo a <a href="/facts/Pseudorotation/qEBkqgQP">pseudorotational</a> rearrangement called the <a href="/facts/Bartell_mechanism/PLKV7D5e">Bartell mechanism</a>, which is like the <a href="/facts/Berry_mechanism/Wd7tbwHJ">Berry mechanism</a> but for a heptacoordinated system.
</p><p>Below 4.5 °C, IF7 forms a snow-white powder of colorless crystals, melting at 5-6 °C.  However, this melting is difficult to observe, as the liquid form is thermodynamically unstable at <a href="/facts/760_mmHg/aTbYALII">760 mmHg</a>: instead, the compound begins to <a href="/facts/Sublimation_(phase_transition)/KDoKokMn">sublime</a> at 4.77 °C.  The dense vapor has a mouldy, acrid odour.
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Iodine heptafluoride open-in-new

Iodine heptafluoride