the quantum model of the atom. objectives discuss louis de broglie’s role in the development of...
TRANSCRIPT
The Quantum Model of the
Atom
Objectives
Discuss Louis de Broglie’s role in the development of the quantum model of the atomCompare & contrast the Bohr model and the quantum model of the atomExplain how the Heisenberg uncertainty principle and the Schrödinger wave equation led to the idea of atomic orbitalsList the four quantum numbers, and describe their significanceRelate the number of sublevels corresponding to each of an atoms main energy levels, the number of orbitals per level, and the number of orbitals per main energy level
To SummarizeNeils Bohr--Planetary model—electrons arranged in circular paths (orbits) around the nucleus Answered Rutherford’s ?—electrons in a particular path have a fixed energy, they do NOT lose energy and fall into the nucleus Energy level—region around nucleus where it is likely to be moving, similar to rungs on a ladder but not equally spaced Quantum—amount of energy needed to move an electron from its current energy level to the next higher one
Electrons as Waves
Louis de Broglie—French scientist-1924
Electrons had a dual wave-particle nature also
Waves can have only certain frequencies
Electron waves have specific energies (frequencies)—Bohr orbits
The Heisenberg Uncertainty Principle
Werner Heisenberg—German physicist-1927
Where are the electrons?Detecting electrons with light (photons) interferes with its current pathHeisenberg uncertainty principle—it is Heisenberg uncertainty principle—it is impossible to determine both the impossible to determine both the position and velocity of an electron at position and velocity of an electron at any one timeany one timeDifficult for scientists to accept at the time
Schrödinger Wave Equation
Erwin Schrödinger—Austrian physicist—1926
Used math and quantum theory to describe locations of electrons
Few if any analogies
States the probability of finding an electron in a certain position—blurry cloud
OrbitalsOrbitals have quanta of energy but electrons do not have specific locations
Atomic Orbitals & Quantum Numbers
OrbitalOrbital: 3-D region that indicates probable location of an electron
Quantum numbers—specify the properties of atomic orbitals and the electrons they contain
Orbitals have different shapes and sizesPrincipal quantum numberPrincipal quantum number, angular momentum quantum number, magnetic quantum number, spin quantum number
Principal Quantum Number
Symbol: nIndicates the main energy level of the electronValues are positive whole numbers only1, 2, 3, etc.Lower numbers mean lower energy levelsEach main energy level has sublevels
OrbitalsSeveral electron cloud shapes are possible because energy levels are divided into energy sublevels
Each cloud shape is an atomic orbital—region in space where there is a high probability of finding an electron
ss orbitals are spherical
pp orbitals are dumbbell shaped
dd and ff orbitals are more complex
See p. 102-103
Orbitals
ss sublevel has one orbital
pp sublevel has three orbitals
dd sublevel has five orbitals
ff sublevel has seven orbitals
Each orbital can only have 2 electrons
http://home.montgomerybell.edu/%7Eneergaj/atomorbs.html
Pictures of orbitals
http://winter.group.shef.ac.uk/orbitron/
http://www.glencoe.com/sites/common_assets/science/cmc/cim/animations/ch5_2.rm
Animation of orbitals & electron emission spectra