1. Chem-To-Go Lesson 7 Unit 2 ENERGY OF ELECTRONS

2. ENERGY BASICS All energy travels in the form of a wave. Scientists measure the wavelength of a wave to identify its type of energy. Four Important Wave Words: Wavelength (λ) Frequency (ν) Energy (E) Speed of light (c) Two Important Equations: 1)c = λν 2)E = hν c = 3.0x10 8 m/s h= 6.626x10 -34 J·s

3. ENERGY BASICS The spectrum includes all forms of energy. We’ll focus mainly on the VISIBLE SPECTRUM. Notice that RED has the longest λ but the lowest v. Notice that VIOLET has the shortest λ but the highest v. c = 3.0x10 8 m/s for ALL

4. CONNECTION TO ATOMIC STRUCTURE ABSORPTION Atoms, specifically the electrons, can absorb photons of energy. With higher energy, the electron must move from its normal energy level [ground state] to a higher energy level in the electron cloud [excited state]. The excited state is temporary. PHOTON – a quantum or “piece” of energy GROUND STATE – lowest allowable energy level for a certain electron EXCITED STATE – temporary high energy level for a certain electron

5. CONNECTION TO ATOMIC STRUCTURE EMISSION Eventually, the electron must release [emit] the energy that it has recently absorbed. The emitted photon of energy will leave the atom in the form of a light wave. If the wave’s wavelength falls between 400 and 700 nm, then it will be visible light. This emission of light in the visible spectrum is how we create fireworks.

6.  Useful to know how much energy is coming out of an atom  Useful to know how much energy to put into an atom to achieve a particular color USEFUL TO CALCULATE THE ENERGY c = λν c = 3.0x10 8 m/s E = hν h= 6.626x10 -34 J·s

7.  An atom emits a photon of green light with wavelength of 650 nm. How much energy does the photon carry? CALCULATING THE ENERGY, WAVELENGTH, OR FREQUENCY OF LIGHT