Gr.10_Chem_PPT_Ch.7_L.3_Bohr's theory of hydrogen atom (1)

Chapter Overview

  • Title: Atomic Structure and Periodicity

  • Authors: Jason Overby, Raymond Chang

  • Edition: Fourteenth Edition (Mc Graw Hill)

Essential Questions

  • Bohr model of hydrogen atom

  • Can we determine the exact location of an electron? Why or why not?

  • Definitions: orbital, electron configuration, shielding, Aufbau principle

Learning Objectives

  • Understand Bohr model and its explanation of atomic emission spectra in hydrogen.

Atomic Models Timeline

  • Understanding electron locations involves indirect methods since inner structures are not visible directly.

Wave-Particle Duality of Light

  • Light exhibits properties as both wave and particle (photon).

  • Key Concepts:

    • Wavelength

    • Frequency

    • Quantum energy carried by photons

Wave Properties

  • Characteristics of waves:

    • Wavelength, frequency, amplitude

    • Speed (c) relationship: c = frequency × wavelength

  • Inverse relationship between wavelength and frequency.

Calculating Frequency

  • Example: Calculate frequency for 686 nm wavelength.

Electromagnetic Radiation Categorization

  • Categorize radiation based on wavelength:

    • Ultraviolet, X-rays, Infrared, Microwave, Radio waves, etc.

Photoelectric Effect

  • Electrons are emitted from metal when illuminated by light.

  • Photon: particle of light with energy proportional to frequency.

Photonic Energy Formula

  • Energy of photon: ( E_{photon} = hν )

    • Where: ( h = 6.626 x 10^{-34} J.s )

Historical Perspective on Emission Spectrum

  • Newton’s work in the 17th century discovered sunlight's color components.

  • Spectrum: observable band of colors from light refraction.

  • Emission: production and release of light.

Characteristics of Emission Spectra

  • Types of spectra:

    • Continuous spectrum: all visible light wavelengths.

    • Line spectra: specific visible light wavelengths.

  • Emission spectra vary for different substances.

Emission Spectrum of Hydrogen Atom

  • Energy transition leads to electron jumps between energy states: ground state and excited state.

  • Emission of light (photons) occurs when electrons return to lower energy levels.

Characteristics of Energy Levels

  • Ground state (n=1): lowest, stable energy.

  • Excited states (n>1): higher energy, unstable.

  • Emission spectrum provides unique identification for each element.

Energy Transition Formula

  • Energy of photon emitted during electron transition: ( n_{i} \rightarrow n_{f} )

    • Use Rydberg constant ( R_H = 2.18x10^{-18} ).

Review Questions

  • Energy Levels: Distinguish ground state vs. excited state.

  • Emission Spectra: Define and differentiate line from continuous spectra.

  • Bohr's Theory: Explain hydrogen atom emissions and differences from classical physics principles.