1. electromagnetic radiation – transmission of energy through space in the form of oscillating waves wavelength, – distance between identical points on successive waves

2. frequency, ν – # times per second a wavelength moves past a point 0 1 2 (sec) Heinrich Hertz 1857-1894 units for v = 1 sec 1 sec = Hertz or Hz ν = 1 1 sec ν = 1 Hz

3. All electromagnetic radiation travels at the same velocity: the speed of light, or c. c = 3.00  10 8 m/sec · ν (m) · (1/sec) = m/sec c = ·ν

4. The entire electromagnetic spectrum

6. Max Planck 1858-1947 1900 Planck: “atoms absorb or release energy in ‘discrete’ (or fixed) amounts”. quantum – the smallest amount of energy an atom can absorb or release

7. quantized – only certain, fixed energies are allowed continuous – any energy is allowed continuousquantized

8. Albert Einstein 1879-1955 1905 Einstein: “light exists as a tiny particles” photon – the smallest particle of electromagnetic radiation (or light)

9. E = h ν h = Planck’s constant h = 6.626 x 10 - 34 J·sec E = energy of a photon

10. How much energy (in Joules) does a photon of 555 nm possess ? 1 m = 1 x 10 9 nm c = ν E = h ν E = hc

11. continuous spectrum – a rainbow where one color continually bleeds into the next

13. emission spectrum – light emitted from an excited species

14. Hydrogen discharge tube resulting line spectrum line spectrum – light of only certain wavelengths (or colors) are observed

15. The line spectrum of hydrogen The line spectrum of sodium The line spectrum of neon

16. Niels Bohr 1885-1962 n distance from nucleus 153 pm 2212 pm 3476 pm 4846 pm 51323 pm quantized – restricted to certain, fixed values or places

17. The Bohr Model of the Atom Electrons “orbit” the nucleus at a fixed distance. The electron may have ONLY the energy of the specific orbit.

18. ground state – e - in atom are in the lowest energy state possible (closest to the nucleus) excited state – e - in atom are promoted to higher energy states (further from the nucleus) absorb E release E n = 1 n = 2 (or higher)

19. when an electron returns from the excited state back down to the ground state, it releases (or emits) energy in the form of a photon of light the wavelength (or color) of the photon is indicative (or representative of) the energy difference (or gap) between the orbitals where the transition occurred

20. Transitions between Quantized Levels excitation (absorb energy) emission (release energy) n = 1 n = 2

21. but why different photons ? ex. hydrogen has 4 different lines red photon with = 656 nm turquoise photon with = 486 nm purple photon with = 434 nm

22. Real Story !