The Bohr Model of the Atom: Bohr’s major idea was that the energy of the atom was quantized, and that the amount of energy in the atom was related to the electron’s position in the atom. quantized means that the atom could only have very specific amounts of energy.

Electromagnetic Radiation: light is one of the forms of energy technically, light is one type of a more general form of energy called electromagnetic radiation electromagnetic radiation travels in waves every wave has four characteristics that determine its properties – wave speed, height (amplitude), length (wavelength), and the number of wave peaks that pass in a given time (frequency).

Electromagnetic Waves: Wavelength (λ): Is the distance between two crests (cm). Frequency (ν): Is the of crests that pass by one point every second (1/s or s -1 or Hz ). ( Hertz)

The speed of light (c) in vacuum is a universal physical constant. Its value is exactly meters per second ≈3.00×10 8 m/s or 3.00×10 11 cm/s c = λ x ν E = h ν Energy Plank’s Constant ( x J.s) (J = kg m 2 /s 2 ) Joule (J) ( x kg m 2 /s )

5 c = λ x ν

Exercise # 2: Calculate the frequency of a light if its wavelength is 640 nm. c = λ ν c = x 10 8 m/s λ= λ=640 nm = 6.40 x m (1 nm =10 -9 m) ν = x 10 8 m/s 6.40 x m ν =0.468 x s -1 ν =4.68 x s -1 or 4.68 x Hz (Hertz) ν = c / λ→ ÷

Exercises # 2: Calculate the energy of a light if its frequency is 4.68 x s -1 E = h ν h = x J.s E = 31.0 x J E =3.10 x J ν =4.68 x s x J.s x 4.68 x s -1

Light’s Relationship to MatterLight’s Relationship to Matter: Atoms can acquire extra energy, but they must eventually release it When atoms emit energy, it always is released in the form of light. However, atoms don’t emit all colors, only very specific wavelengths. In fact, the spectrum of wavelengths can be used to identify the element.

Electromagnetic Spectrum:

Visible light: Infrared rays -- lowest energy Ultra Violet rays -- highest energy (Greater wavelength & smaller frequency) (Smaller wavelength & greater frequency) E = h ν