CHEM H90 Lecture 8: Lecture #8
How the Periodic Table Gets its Shape
• s orbitals
o spherical
o have L=0
o 90% chance of finding electron inside the ball
• p orbitals
o dumb bell shape (2 spheres)
o have L= 1
o 90% chance electron is inside either sphere
o 3 p orbitals
• d orbitals
o L =2
o 5 d-orbitals
o same shape for every atom
• historical names for shapes of orbitals
o l=0 is s orbital and spherical
o l= 1 is p orbital and dumbbell shape
o l =2 d orbital
o l=3 is f orbital
• another quantum number
o electron spin quantum number (ms)
o Pauli’s principle
▪ in a particular atom, no two electrons can have the same set of quantum
numbers
o electrons in the same orbital have the same values for n, l, and ml, so they must have
different values for ms
• orbital occupation
o how many electrons fit into 1 orbital?
o only 2 electrons fit into 1 orbital
▪ 1 spin up
▪ 1 spin down
• pattern emerges
o for each value of l, there are 2/+1 orbitals
o for each value of n, l ranged from 0 to n-1
o for each n, there are n2 orbitals
o for each n, electrons have 2n2 places to go
o if n is 1, 2n2 is 2
o if n is 2, 2n2 is 8
• a very deep thing
o everything in our material world is made from atoms
o all the interesting stuff happens because you can combine their electrons in almost
infinitely many ways
o all their chemical properties are determined by their position in periodic table
o the shape of the periodic table is due to quantum mechanics
• what we should have learned
o electron ‘orbits’ described by wavefunctions
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