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Intermolecular Forces (Melting Pts.)

Posted: Thu Nov 29, 2018 9:04 pm
by Steven Garcia 1H
CHI3 has a higher melting point than CHF3 for reasons of polarizability (larger atom will increase London interactions), which I understand, but doesn't CHF3 have a larger dipole moment (thus stronger dipole-dipole interactions) than the CHI3 molecule because F is more electronegative than I? Does this not matter?

Re: Intermolecular Forces (Melting Pts.)

Posted: Thu Nov 29, 2018 9:41 pm
by Shash Khemka 1K
A simple way to consider melting points is larger atom → more electrons → higher polarizability (easily distortable electron cloud) → stronger intermolecular bond → higher boiling/melting point.

CHI3 is a larger atom compared to CHF3. Regarding the electronegativity question, I don't think it matters as much when considering boiling or melting points. The size of the molecule, as well as the polarizability of it, determine its boiling/melting point.

Re: Intermolecular Forces (Melting Pts.)

Posted: Wed Dec 05, 2018 8:54 pm
by Vana Mirzakhani 3I
To add on, as atomic size increases, surface area of the atom also increases, leading to a higher melting point for CHI3 rather than CHF3.