Physics Question #2791

D. Andrew White, a 43 year old male from Toronto asks on June 2, 2005,

Do different isotopes vary slightly in chemical properties? Or are they the same? i.e. are the orbital energies somewhat different because of charge distribution via nuclear size - or such not? I have heard conflicting things. Some people who have said yes were clearly talking of physical properties, such as evaporation rates ( which I already know about).

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The answer

Mike Thewalt, Physics Professor, Simon Fraser University, BC answered on June 3, 2005

I would not think that the chemical properties (reaction rates, energies involved in chemical reactions, etc.) would be different to a degree which is measurable. The electronic properties (energies of ground and excited states) are different enough to be measured, but this is because these energies, or more exactly, the difference in energies between different levels, can be measured with such extreme accuracy using spectroscopy. Also, different isotopes of the same element can have different nuclear spins, which can also affect the electronic energy levels, with non-zero nuclear spin isotopes having splitting of the electronic levels via the hyperfine interaction. Still, while these effects are visible using high resolution spectroscopy, I would not expect them to change the chemical behavior in measurable ways.

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