1. Waves & Particles Electrons in Atoms

2. Electrons Electrons which are negatively charged, travel around the nucleus (the center of the atom).

3. Waves A crest origin trough

4. Waves Wavelength ( ) - length of one complete wave Frequency ( ) - # of waves that pass a point during a certain time period hertz (Hz) = 1/s Amplitude (A) - distance from the origin to the trough or crest

5. Electromagnetic Radiation Three primary characteristics: Wavelength ( ) Frequency ( ) Speed (speed of light = c) Wavelength and Frequency are inversely proportional, meaning: The shorter the wavelength the higher the frequency. With that we come up with the following equation: = c

6. Electromagnetic Radiation Calculate the frequency of red light of wavelength 6.50x10 2 nm. The unit with which we are left, 1/s (inverse seconds), also referred to as hertz (Hz).

7. Electromagnetic Radiation Using Planck’s constant (h), which equals 6.626x10 -34 J s, we can calculate the change in energy for a system (ΔE) using the following equation: ΔE = h This equation proves that energy exists in small “packets” called quantum.

8. Electromagnetic Radiation The blue color in fireworks is often achieved by heating copper(I) chloride (CuCl) to about 1200°C. Then the compound emits blue having a wavelength of 450 nm. What is the increment of energy (the quantum) that is emitted at 450 nm by CuCl?

9. EM Spectrum LOWENERGYLOWENERGY HIGHENERGYHIGHENERGY

10. LOWENERGYLOWENERGY HIGHENERGYHIGHENERGY

11. Quantum Theory Planck (1900) Observed - emission of light from hot objects Concluded - energy is emitted in small, specific amounts (quanta) Quantum - minimum amount of energy change

12. Quantum Theory Planck (1900) vs. Classical TheoryQuantum Theory

13. Einstein (1905) Observed - The Photoelectric EffectThe Photoelectric Effect

14. Quantum Theory Einstein (1905) Concluded - light has properties of both waves and particles “wave-particle duality” Photon - particle of light that carries a quantum of energy

15. Bohr Model of the Atom Electrons in Atoms

16. A. Line-Emission Spectrum ground state excited state ENERGY IN PHOTON OUT

17. B. Bohr Model 1 2 3 4 5 6 Energy of photon depends on the difference in energy levels Bohr’s calculated energies matched the IR, visible, and UV lines for the H atom

18. Other Elements Each element has a unique bright-line emission spectrum. “Atomic Fingerprint” Helium