1. Atomic Structure & Periodicity
Chapter 7

2. EM Radiation
EM – electromagnetic
Wavelengths measured in meters

3. Properties Energy decreases  Frequency decreases 
Wavelength increases 
Speed is constant 
x 108 m/sec

4. Properties Relationship Wavelength (λ) Frequency (ν) Speed (c)
Distance between two consecutive peaks or troughs in a wave
Measured in m
Frequency (ν)
Number of waves that pass a given point per second
Measured in hertz
Hz = sec-1
Speed (c)
Measured in m/s
Relationship
λ ν = c

5. Nature of Matter Max Planck & Quantum Theory
Energy is gained or lost in whole number multiples of the quantity hν
Frequency = ν
Planck’s constant = h = x Js
ΔE = hν
Energy is transferred to matter in units of energy called quanta
Einstein and the Particle Nature of Matter
EM radiation is a stream of particles – photons
Photon – “packet” of EMR energy
Ephoton = hν = hc/λ
Energy and mass are inter-related
E = mc2

6. Nature of Matter de Broglie and the Dual Nature of Light
Light travels through space as a wave
Light transmits energy as a particle
Particles have wavelength, exhibited by diffraction patterns
Large particles have very short wavelengths
All matter exhibits both particle and wave properties
EMR e Baseball
Wave Wave/Particle Particle

7. Atomic Spectrum of H Continuous spectra Bright line spectra
Contains all wavelengths of light
Bright line spectra
Excited electrons in an atom return to lower energy states
Energy is emitted in the form of a photon of definite wavelength
Definite change in energy corresponds to
Definite frequency
Definite wavelength
ΔE = hν = hc/λ
Only certain energies are possible within any atom

9. Bohr Model (Niels Bohr 1913)
Quantum Model
The electron moves around the nucleus only in certain allowed circular orbits
Bright line spectra confirms that only certain energies exist in the atom
Atom emits photons with definite wavelengths when the electron returns to a lower energy state
Energy levels available to the electron in the hydrogen atom
ΔE = x J (Z2/n2)
n = an integer
Z = nuclear charge
J = energy in joules

10. Bohr Model Calculating the energy of the emitted photon
Calculate electron energy in outer level
Calculate electron energy in inner level
Calculate the change in energy (ΔE)
ΔE = Efinal – Einitial

11. ( ) Bohr Model Energy Change in Hydrogen Atoms
Calculate energy change between any two energy levels
ΔE = x J n2final n2initial
Shortcomings of the Bohr Model
Bohr’s model does not work for atoms other than hydrogen
Electrons do not move in circular orbits
( )