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Chapter 7 Atomic Structure and Periodicity - PowerPoint PPT Presentation

Chapter 7 Atomic Structure and Periodicity. 7.1-7.2 7.3-7.4 7.5-7.8 7.9-7.11 7.13. Properties of Light. Electromagnetic radiation- the way energy travels through space. This energy travels at the speed of light. Waves. Three characteristics: 1.Wavelength 2.Frequency 3. Speed

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Chapter 7 Atomic Structure and Periodicity

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Chapter 7Atomic Structure and Periodicity

7.1-7.2

7.3-7.4

7.5-7.8

7.9-7.11

7.13

Properties of Light

• Electromagnetic radiation- the way energy travels through space.

• This energy travels at the speed of light.

Waves

• Three characteristics:

• 1.Wavelength

• 2.Frequency

• 3. Speed

• Wavelength =distance between two peaks (in meters)

• Frequency = number of waves per second (cycles per second)

• Speed= travels at speed of light (meters per second)

continued

• Inverse relationship b/t. frequency and wavelength.

• Examples:

7.2 Nature of Matter

• Planck discovered:

• Energy is gained or lost in whole number quantities of hv

• Planck’s constant h = 6.626 x 10-34 J.s

• So Planck determined that energy is quantized (measured) in small packets called hv.

Energy of a Photon

• Change in energy can be calculated by:

• Delta E = nhv

• n = intergers (1,2,3…)

• h = 6.626x10-34 J.s (Planck’s constant)

• v = frequency of EM radiation absorbed or emitted.

A Photon

• Einstein viewed electromagnetic radiation as travelling in a stream of particles called “photons”

• E photon = hv= hc/lamda

To summarize….

• Energy is quantized. It occurs in units called quanta.

• Electromagnetic radiation exhibits wavelike properties and particulate properties also.

deBroglie equation

• EM radiation shows wavelike and particulate properties.

• Electrons exhibit particulate and wavelike properties.

• m = h/lamdav or lamda = h/mv

• Examples:

7.3 Atomic Spectrum of Hydrogen

• Excited hydrogen atoms emit light!

• Hydrogen bonds are broken and H atoms release energy….

• Excess energy is released by emitting light of different wavelengths.

Line Spectrum vs. Continuous

• Bohr proposed that an electron orbits the nucleus in a rigidly defined energy level.

Energy Atom = E photon = E e-final- E e-initial

Continuous Spectrum

• White light is a contiuous spectrum.

• The Hydrogen Emission Spectrum is a LINE spectrum

• Atoms in excited states exhibit line spectrum not continous spectrum.

E = -2.178 x 10-18(Z2/n2)

Z= nuclear charge

n = the size of the radius (the larger the value of n, the larger the orbit radius)

(-) sign means: energy of the electron bound to the nucleus is lower than if electron were at infinity.

At infinite distance, no interaction occurs and the energy is zero.