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 = l n• 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• E

photon = 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!