Chapter 5 Electronic Structure and Periodic Trends

1. Chapter 5 Electronic Structure and Periodic Trends 5.1 Electromagnetic Radiation Learning Goal Compare the wavelengthof radiation with its frequency.

2. Chapter Readiness Key Math Skills • Solving Equations (1.4D) Core Chemistry Skills • Using Prefixes (2.5)

3. Electromagnetic Radiation We experience electromagnetic radiationwhen we • listen to a radio • use a microwave oven • see colors in a rainbow • have an X-ray taken All types of electromagnetic radiation, including light, consist of particles that move as wavesof energy.

4. Wavelength and Frequency Waves of electromagnetic radiation are similar to waves you might see at the beach. The highest part of the wave is called a crest, and the lowest point is called a trough. Wave Crest Wavelength, λ (lambda) Wave Trough

5. Wavelength and Frequency

6. Wavelength and Frequency Frequency (symbol ν, nu) • is the number of times the crests of a wave pass a point in one second • is measured in hertz (Hz), equal to cycles/second or s−1 All electromagnetic radiation travels at the speedof light (c), 3.00 × 108 m/s.

7. Wave Equation The wave equation expresses the relationship of the speed of light (m/s) to wavelength (m) and frequency (s−1). c = λν Speed of light (c) = 3.00 × 108 m/s = wavelength (λ) × frequency (ν) = wavelength (m) × frequency (s−1)

8. Electromagnetic Spectrum The electromagnetic spectrum is an arrangement of different types of radiation from the longest to the shortest wavelength. As the wavelength increases, the frequency decreases. The speed of light (c) is constant. λ

9. Inverse Relationship of λ and ν The inverse relationship of wavelength andfrequency means that • longer wavelengths have lower frequencies • shorter wavelengths have higher frequencies • different types of electromagnetic radiation have different wavelengths and frequencies

10. Electromagnetic Spectrum The longer wavelengths include radio waves and those from cellular phones, while shorter wavelengths are produced from infrared lights, ultraviolet light, and heat lamps. Visible light ranges from 700 to 400 nm.

11. Electromagnetic Spectrum

12. Learning Check Short wavelengths of blue are dispersed more by the molecules in the atmosphere than longer wavelengths of visible light, which is why we say the sky is blue. If blue light has a wavelength of 450 nm, is the wavelength of red light greater or less than 450 nm? 400 nm 700 nm

13. Solution The wavelength of red light is greater than that of blue light, which means that the wavelength of red light is greater than 450 nm.

14. Learning Check If the frequency of blue light is 6.3 × 1014 Hz,what is its frequency in kilohertz (kHz) and inmegahertz (MHz)?

15. Solution If the frequency of blue light is 6.3 × 1014 Hz,what is its frequency in kilohertz (kHz) and inmegahertz (MHz)?