Friday, August 3, 2018

physical chemistry - How does absorption spectroscopy work?


So a beam of white-light photons passes through a gas and various photons, having exactly the same energy as the gas's molecular energy transition state deltas, get absorbed. We then get a characteristic absorption pattern. But wait a minute, don't the energised electrons fall back to their ground states within a nanosecond and create photons of precisely the same energy as those that caused the disturbance? How come we still see the absorption band?




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periodic trends - Comparing radii in lithium, beryllium, magnesium, aluminium and sodium ions

Apparently the of last four, $\ce{Mg^2+}$ is closest in radius to $\ce{Li+}$. Is this true, and if so, why would a whole larger shell ($\ce{...