Chapter 7 The Quantum Mechanical Model of the Atom · Tro: Chemistry: A Molecular Approach, ... 11....
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Copyright 2011 Pearson Education, Inc. Tro: Chemistry: A Molecular Approach, 2/e Radiation • Particles and rays emitted by radioactive material • ALPHA (α): 2 4 He 2+ • BETA (β): 0 0 − (high speed electron) • GAMMA (γ): gamma rays 1 Tro: Chemistry: A Molecular Approach, 2/e
Transcript of Chapter 7 The Quantum Mechanical Model of the Atom · Tro: Chemistry: A Molecular Approach, ... 11....
Copyright 2011 Pearson Education, Inc.Tro: Chemistry: A Molecular Approach, 2/e
Radiation
• Particles and rays emitted by radioactive
material
• ALPHA (α): 24He2+
• BETA (β): 00𝜷−
(high speed electron)
• GAMMA (γ): gamma rays
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Nature of Light:
Wave Nature
• Light is a form of Electromagnetic Radiation
Composed of perpendicular, oscillating waves:
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Characterizing Waves
• Wave length (λ): distance from crest to crest (m)
• Amplitude: height of the wave (brightness)
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Characterizing Waves
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Characterizing Waves
• Frequency (ν): # of waves past a point in a
given period of time.
• Units: Hz (hertz) which means 1
𝑠or 𝑠−1
• Energy (E): Proportional to the frequency (ν).
E = 𝒉ν
• ℎ = 𝑃𝑙𝑎𝑛𝑐𝑘′𝑠 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 = 6.626 × 10−34𝐽
𝐻𝑧
• High frequency = High E
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Relating Frequency and Wavelength
• Speed of Light (c): speed of light is constant
𝒄 = 3.00 × 108𝑚
𝑠• λ and ν are inversely related (as one gets
bigger, the other gets smaller)
𝒄 = 3.00 × 108𝑚
𝑠= 𝝀𝝂
• If you know one (λ or ν) you can find the other
𝝀 =𝒄
𝝂𝝂 =
𝒄
𝝀
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Example Calculation
• What is the wavelength of light (in m) whose
frequency is 7.500 x 1012 Hz?
• 𝒄 = 𝝀𝝂 so 𝝀 =𝒄
𝝂
• 𝝀 =𝒄
𝝂=
3.00×108𝑚
𝑠
7.500×1012𝐻𝑧
• = 4.00 × 10−5𝑚
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The Electromagnetic Spectrum
• electromagnetic spectrum – all the
wavelengths of light.
• Visible Light makes up a only a small fraction
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Continuous Spectrum
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Spectra
• When atoms or molecules absorb energy, that
energy is often released as light energy
• Emission Spectrum – light emitted is passed
through a prism.
non-continuous: doesn’t have all wavelengths
Unique: can be used to identify the material
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Exciting Gas Atoms to Emit Light
with Electrical Energy
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Identifying Elements with
Flame Tests
Na K Li Ba
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Emission Spectra
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Examples of Spectra
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Emission vs. Absorption Spectra
Spectra of Mercury
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