Question

1. model 2 shows the emission spectra for hydrogen and boron. scientists can also record the absorption spectra for elements. propose how this might be done, and what the absorption spectra of hydrogen and boron would look like.

Explanation:

To create an absorption spectrum, shine continuous white light (containing all wavelengths) through a cool, low-density sample of the element (hydrogen or boron) in its gaseous state. The cool gas atoms will absorb specific wavelengths of light corresponding to the energy needed to excite their electrons to higher energy levels. When the transmitted light is passed through a spectrometer, the absorbed wavelengths will appear as dark lines against a bright continuous background.

For hydrogen and boron, the dark lines in their absorption spectra will occur at exactly the same wavelengths as the bright emission lines in their respective emission spectra. This is because the energy gaps between electron energy levels are fixed for each element—absorption uses the same discrete energy values (and thus same wavelengths) as emission, just in reverse (electrons absorb energy to jump up, rather than releasing energy to fall down).

Answer:

1. How to record absorption spectra: Shine continuous white light through a cool, low-density gaseous sample of hydrogen or boron, then pass the transmitted light through a spectrometer to detect the resulting spectrum.
2. Appearance of absorption spectra:

• Hydrogen's absorption spectrum will be a continuous bright spectrum with dark lines at the exact same wavelengths as the bright lines in hydrogen's emission spectrum.
• Boron's absorption spectrum will be a continuous bright spectrum with dark lines at the exact same wavelengths as the bright lines in boron's emission spectrum.