# Atoms
## A8 Why even do spectroscopy
**a)** Why do we do IR spectroscopy on synthetized compounds? Which bands are excited? Which mathematical model would fit the energy distribution?
**b)** Why do Physicists do spectroscopy on Atoms?
**c)** Imagine you wanted to determine the composition of a star, how would you go about it?
## A9 Just vibin
**a)** A molecule has an absorption peak at a wavelength of 400 nm. What is the corresponding frequency in Hz?
**b)** A hydrogen atom undergoes a transition from the n = 4 to n = 2 energy level. Calculate the wavelength of the emitted photon.
## A10 Orbital overload
**a)** Explain what an orbital is to: A child, Yourself a year ago, Yourself
**b)** What do the colors of the orbitals mean mathematically
**c)** Draw the occupied orbitals and their electrons for the Termsymbol $^{3}P_{0}$