## Interaction Potential Energy and Radius

KDang_1D
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### Interaction Potential Energy and Radius

If interaction potential energy is given by the formula: Ep (is proportional to) $\frac{\alpha_{1} \alpha_{2} }{r^{6}}$, then why does attractive force increase as atomic size increases?

Sebastian Lee 1L
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### Re: Interaction Potential Energy and Radius

When atomic size increases, polarizability ($\alpha$) increases because the electrons are held on less tightly by the nucleus. High polarizability creates the stronger intermolecular forces described by the larger interaction potential energy. The distance between molecules is important but I think that atomic radius has a much more significant effect on polarizability than it does on the distance between molecules. Note that the inverse proportionality to r is relevant when discussing shape (rod vs sphere) because a rod shape will have closer dipole moments and thus a stronger interaction energy.

Rohit Ghosh 4F
Posts: 99
Joined: Thu Jul 25, 2019 12:17 am

### Re: Interaction Potential Energy and Radius

Although polarizability is a factor in determining potential energy, the distance between molecules is much more important due to that value being to the power of 6.