Electrons can move up and down to different orbitals or shells based on absorbing or releasing of energy. 

Bohr's Model of the Atom

Concept #1: Understanding the Atom

Bohr's Model tries to explain what happens to the electron when it absorbs or emits energy. 

Concept #2: Absorption vs. Emission

In absorption, an electron gains energy and becomes excited. In this excited state, the electron moves to higher energy level. 

In emission, the electron releases its excess energy to go down to a lower energy level.

Example #1: Calculate the energy of the 4th electron found in the n = 2 state of the boron atom in kilojoules per mole. 

Practice #1: Which of the following transitions (in a hydrogen atom) represents emission of the longest wavelength?

Practice #2: Which of the following transitions represents absorption of a photon with the largest energy?    

Atomic Emission

Concept #3: Understanding Absorption & Emission

Concept #4: Different Emission Series

We know that emission is the releasing of energy, but different energies are released depending on which shell the electron falls. These different energies appear in different places on the electromagnetic spectrum. 

Example #2: What is the wavelength of a photon (in nanometers) emitted during a transition from n = 4 to n = 2 state in the hydrogen atom?

Practice #3: Classify each of the following transitions as either a Lyman, Balmer or Paschen series. a) n = 3 to n = 1 b) n = 6 to n = 1 c) n = 3 to n = 2 d) n = 6 to n = 3 e) n = 4 to n = 2