Download Chapter 4: Electron Configurations

Chapter 4: Electron
Configurations
Development of New Atomic Model
Properties of Light
• Light emission/absorption
– Electromagnetic spectrum
• g rays, X rays, UV-visible-IR, microwave/radar, radio
waves (TV, FM, Short wave), long waves
• Light as a wave
– Electromagnetic radiation acts like a wave
• c=ln
• speed of light = (wavelength)(frequency)= 3 x 108 m/s
– Wavelength is inversely proportional to frequency
• Interference, diffraction, refraction, & reflection
Electromagnetic Radiation Spectrum
Wave’s Anatomy
Properties of Light, continued
• Light as a particle
– Photoelectric effect
• Emission of electrons from metal when light hits it
• Red light’s frequency is too low to excite electrons
– Quantum of energy
• Minimum amount of energy lost/gained by an atom
• Quantum = small, specific packet of energy
– “Photon” : term coined by Einstein
• Particle of electromagnetic radiation, no mass, 1 quantum
• Energy of photon = (Plank’s constant)(frequency)
• E photon = h n; h = 6.626 x 10-34 Joule second, n = 1/sec
H-atom Line-Emission Spectrum
• Electricity through low pressure gas increases
atoms’ potential energy (excited states)
• Atoms have only 1 ground state
• When atoms return to ground state, they emit
that extra energy as electromagnetic radiation
• Hydrogen shows specific bands (l)
– Balmer series – visible (4 lines/ colors for H)
– Lyman series – ultraviolet (5 lines for H)
– Paschen series – infrared (3 lines for H)
Hydrogen Visible Light Spectrum
Quantum Model of the Atom
• Shows why H atoms emit specific frequencies
• Ephoton = E2 – E1 = h n
– Energy of photon equals difference between
excited & ground states
– Absorption = added energy moving e- to higher E
– Presence of specific bands => fixed energy levels
– Electrons only exist is very limited energy states
– Niels Bohr’s model: electrons go in defined orbits
De Broglie’s Hypothesis
• Electrons have dual wave-particle nature too
• Any wave confined to a space has limited n
• Electron beams behaved as waves empirically
– Diffraction = bending of waves passing by edges
– Interference = overlapping waves or energy
– E photon = h n, where n corresponds to Bohr’s orbits
Heisenberg Uncertainty Principle
• Electrons found by interaction with protons
• Photons have ~ same energy as electrons
• Using photons to find electrons kicks e- away
THEREFORE…
• It’s impossible to know both the position &
velocity of electron/ particle simultaneously
Schrodinger Wave Equation
• Treats electrons in atoms as waves
• Only waves of specific energies worked
• Heisenberg’s Uncertainty Principle plus
Schrodinger wave equation  Quantum
theory
• Quantum Theory: mathematical description of
wave properties of electrons & other very
small particles
Quantum Numbers
• Principal Quantum Number
– n = main energy level of the electron
• Angular Momentum Quantum Number
– l = shape of orbital = 0 and n - 1
• Magnetic Quantum Number
– m = orientation of orbital = + l
• Spin Quantum Number
– s = spin state = clockwise/counterclockwise= + 1/2
To Be Continued …
• Please absorb this information first, then proceed with the
PowerPoint entitled “Electron Configuration of atoms & ions”
•
Thank you for your attention
•
Have a good day!