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An atom moving at its root-mean-square speed at $\pu{20 °C}$ has a wavelength of $3.28×10^{-11}$ m. Identify the atom.
Here's what I did--
$$u_{rms}=\sqrt{\frac{3RT}{M}}$$and $$\lambda=\frac{h}{mu_{rms}}$$$\Rightarrow u_{rms}=\frac{h}{m\lambda}\Rightarrow \sqrt{\frac{3RT}{M}}=\frac{h}{m\lambda}$ ...