# Why aren't atoms affected by gravity, but molecules are?

I read this book here: http://tiny.cc/Gravity-Atom-Myth

It claims that while gravity does affect individual atoms, it's not quantified like molecular mass due to lack of binding proteins which render air-oxygen trajectories improbable.

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Be careful to distinguish between 'does not influence' and 'any influence is too small to accurately measure'. –  David H Oct 18 '13 at 21:28

Just look at the gravitational force between a proton and an electron, where they are $10^{-11}\rm m$ distant, according to Newtonian theory: \begin{aligned} \mathbf F &= \text G \frac{m_e \cdot m_p}{d^2} \\ &= 6.67 \cdot 10^{-11} \frac{9.11 \cdot 10^{-31} \cdot 1.673 \cdot 10^{-27}}{(10^{-11})^2}\\ &= 1.016576701 \cdot 10^{-47} \text{N} \approx 0 \end{aligned}
The force $\bf F$ we calculated is too small that we can literally ignore it, that is, not taking it in account.