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The Development of A New Atomic Model. Ch. 4.1. Properties of Light. Acts like a wave Electromagnetic radiation-wavelike energy traveling through space X-Rays, ultraviolet light, infrared light, radio waves, etc
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Properties of Light • Acts like a wave • Electromagnetic radiation-wavelike energy traveling through space • X-Rays, ultraviolet light, infrared light, radio waves, etc • Electromagnetic Spectrum- organized list of all forms of electromagnetic radiation • All forms travel 3.00 x 108 m/s in a vacuum
Properties of Light Wavelength Frequency λ Distance from crest to crest(or tough to trough) of corresponding waves SI Unit: m, cm, or nm ν # of waves that pass a given point in a specific time SI Unit: Hz
Photoelectric Effect Emission of electrons from a metal when light shines on the metal
Light as a Particle • Quanta • Quantum of energy is the minimum amount of energy that can be lost or gained by an atom • E- energy, J • h- Plancks Constant 6.626 x 10-34 Js • v- frequency, s-1 • Photon • Particle of electromagnetic radiation having zero mass and carrying a quantum energy
The Hydrogen-Atom Line Emission Spectrum Ground State Excited State Lowest energy state of an atom • Atom has a higher potential energy than it does in ground state • Gives off light • Moving from excited back to ground state
The Hydrogen-Atom Line Emission Spectrum Line-Emission Spectrum Continuous Spectrum Narrow beam of light, when passing through a prism Emission of a continuous range of frequencies of electromagnetic radiation
Bohr’s Model of the Hydrogen Atom • Emission • Electron falls to a lower energy level • Photon is emitted • Absorption • Electron jumps from lower to higher energy level • Energy must be added
Electrons as Waves Diffraction Interference Bending of a wave as it passes through a small object • Waves overlap • Different areas have • Reduced energy • Increased energy
Heisenberg Principle It is impossible to determine simultaneously both the position and the velocity of an electron of any other particle
Schrodinger Wave Equation • Quantum Theory • Describes mathematically the wave properties of electrons and other very small particles • Gives the probability of finding an electron in a given orbital • 3 dimensional region around the nucleus that indicates the probable location of an electron
Atomic Orbital's and Quantum Numbers • Quantum Number • Specifies the properties of atomic orbital's and the properties of electrons in orbital's • 1st 3 Numbers • Indicate main energy level, shape and orientation of orbital • 4th Number • “Spin” number describes the fundamental state of the electron that occupies the orbital
Atomic Orbital's and Quantum Numbers Principle Quantum Number • Symbol- n • Indicates main energy level occupied by electron • Positive integers only • 1,2,3, etc • As n increases, distance from nucleus increases • Electrons can have the same value • Same shell • Total orbital's in a shell(main energy level • n2
Atomic Orbital's and Quantum Numbers Angular Momentum Quantum Number • Sublevels • Orbital's of different shapes exist for a given value of n • Symbol- l • Indicates the shape of the orbital • Value • n-1; can be zero or positive integers
Atomic Orbital's and Quantum Numbers Angular Momentum Quantum Number • s orbital • Spherical • p orbital • Dumbbell shape • d & f orbital's • More complex • n=1 • S orbital • n=2 • s & p orbitals • n=3 • s, p, & d orbitals • n=4 • s, p, d & f orbitals
Atomic Orbital's and Quantum Numbers Magnetic Quantum Number • Symbol- m • Indicates the orientation of an orbital around the nucleus • Value • Whole numbers, including zero; -l to +l
Atomic Orbital's and Quantum Numbers Spin Quantum Number • Only 2 Values • +1/2 and -1/2 • Indicates the 2 spin states of an electron in an orbital • Single Orbit • Max of 2 electrons • Must have opposite spin states
Electron Configuration Ch 4.3
Electron Configuration • Arrangement of electrons in an atom • Unique for each element • Ground State Electron Configuration • Lowest energy arrangement of electrons for each element
Rules for Electron Configuration Aufbau Principle Electrons occupy the lowest energy orbital that can receive it
Rules for Electron Configuration Pauli Exclusion Principle No two electrons in the same atom can have the same set of four quantum numbers Arrows represent different spin states
Rules for Electron Configuration Hund’s Rule Orbital's of equal energy are each occupies by one electron before any orbital is occupied by a second electrons All electrons in singly occupied orbital's must have the same spin state
Representing Electron Configurations Orbital Notation Electron Configuration Notation • Unoccupied orbital • ___ • Orbital with 1 electron • ___ • Orbital with 2 electrons • ___ • Quantum # and Sublevel underneath Eliminates lines and arrows Uses superscripts 1s22s22p6
2nd Period Elements • Highest Occupied Energy Level • Electron contained main energy level with the highest principle quantum number • Inner Shell Electrons • Electrons no in the highest occupied energy level
3rd Period Elements • Shorthand Notation • 1st 10 electrons in an atom have the same configuration as Neon • Noble Gas Configuration • Outer main energy level occupied by 8 electrons (most cases)
