Understanding Spectral Lines and Atomic Energy Transitions

CH 26-1

Continuous Spectrum

Emission Spectrum Gas tube View light from a gas tube through a diffraction grating and you will get lines of certain wavelengths that depend on the composition of atoms in the gas tube.

Aborption Spectrum continuous spectrum you will see the continuous spectrum minus lines of certain wavelengths that have been absorbed gas

Spectral Lines The spectral lines depend on the elements (i.e. specific atoms) in the gas and are like a “fingerprint” that tell you the specific atoms present in the gas. The absorption lines are the same wavelengths as the emission lines.

Hydrogen

Helium

Nitrogen

Oxygen

Sodium

Iron

Sun Spectral lines tell us the composition of the atmosphere of Sun.

Calculating spectral lines of hydrogen Rydberg formula where and n is any integer greater than m.

Example If m=2, calculate the spectral lines for n=3, n=4, n=5, and n=6. Which of the integers corresponds to the red (alpha) line?

Photon model of light In 1905, Albert Einstein published a paper explaining the photo electric effect. In this paper, he theorized that light acted as a particle with energy where h is Planck’s constant.

Bohr Model of the atom Neils Bohr developed a planetary model of the hydrogen atom where the electron can only have certain orbits. To go to a higher energy orbit, it must absorb a photon. To go to a lower energy orbit, it emits a photon.

Energy of a H atom The energy of a H atom in a certain orbit n is where n = 1, 2, 3, …

Example What energy photon is absorbed when a hydrogen atom jumps from orbit n=2 to orbit n=3? What wavelength is this photo?

Understanding Spectral Lines and Atomic Energy Transitions