Slide 1 : Four Quantum Numbers:
Specify the “address” (zip code) of each electron in an atom
Slide 2 : First number…Principal Quantum Number ( n)
Energy level (associated with the electron)
Size if orbital
Lowest energy level is assigned principle quantum number of 1 (n=1)
Ground state
What do you think happens as we increase n?
Orbital becomes larger
Electron spends more time farther away from the nucleus? atom’s energy increases
Principle energy levels contain… : Principle energy levels contain… Energy Sublevels
Slide 4 : Principle energy level 1? single sublevel
Principle energy level 2? two sublevels
Principle energy level 3? three sublevels
What pattern do you see in the number of sublevels as we move further away from the nucleus?
They increase as n increases (the further we get from the nucleus)
Slide 5 : Electron’s are labeled according to n value
In atom’s with more than one electron, two or more electron’s may have the same n value
They are in the same “electron shell”
Second quantum number : Second quantum number Angular Momentum Quantum Number (l)
Slide 7 : Each value of l corresponds to a different type of orbital with a different shape
Value of n controls l (subshells possible)
Angular momentum numbers can equal 0, 1, 2, 3…
l=n-1
When n=1, l=0? only one possible subshell
When n=2, l=0,1? two possible subshells
What the number of l means… : What the number of l means… Corresponds to the name of the subshell
L=0? subshell s
L=1? subshell p
L=2? subshell d
L=3? subshell f
S P D F: THE SUBLEVELS : S P D F: THE SUBLEVELS Each of these 4 sublevels has a unique shape
Each orbital may contain at most, 2 electrons
LETTERS ORIGINATED FROM DESCRIPTIONS OF THEIR SPECTRAL LINES
S? sharp…spherical
P? principal…dumbbell shaped
D? diffuse…not all the same shape
F? fundamental…not all the same shape
Slide 12 : When principle energy level n=1, then l=0, which means there is only a single sublevel (one orbital) which is the small, spherical 1s
When principle energy level n=2, then l can equal 0 or 1, which means that there are two sublevels (orbitals) 2s and 2p
2s sublevel? bigger than 1s, still sphere
2p sublevel? three dumbbell shaped p orbitals of equal energy called 2px, 2py, and 2pz
The letters are just there to tell you what axis the electrons go on: x,y, or z axis
When the principle energy level n=3, then l can equal 0,1, or 2, which means that there are 3 possible sublevels:
3s, sphere, bigger than 1s and 2s
3p, dumbbells
3d
Each d sublevel consists 5 orbitals of equal energy
Four d orbitals have same shape but different orientations
Fifth d orbital, 3dz2 is shaped and oriented different from the other four
When the principle energy level n=4, then 1 can equal 0,1,2, or 3 which means l=n-1=4 possible sublevels:
Seven f orbitals of equal energy ( 2 electrons in each orbital)
4s, sphere
4p, dumbbells
4d,
4f
Slide 13 : n = # of sublevels per level
n2 = # of orbitals per level
Sublevel sets: 1 s, 3 p, 5 d, 7 f
Slide 16 : Orbitals combine to form a spherical shape.
Remember… : Remember… 1. Principal # ?energy level
2. Ang. Mom. # ?sublevel (s,p,d,f) There are two more quantum numbers (3 and 4) we will discuss next class
Third Quantum Number : Third Quantum Number Ml? specifies the orientation of the orbital in space containing the electron
Tells us whether the orbital is on the x, y, or z axis
Fourth Quantum Number : Fourth Quantum Number Ms? related to the direction of the electron spin
Tells us if electron has a clockwise spin or counter clockwise spin
Specifies orientation of electrons spin axis
Recap… : Recap… Bohr?
Orbits explained hydrogen’s quantized energy states
De Broglie?
Dual particle and wave nature of electrons
Schrodinger?
Wave equation predicted existence of atomic orbitals containing electrons
Electron Configuration : Electron Configuration Definition: arrangement of electrons in an atom
Basic rules for filling up orbital's with electrons
Which is more stable, low energy or high energy?
So which orbitals are going to be filled up first?
We are going to want an arrangement that gives us the lowest possible energy
Ground state electron configuration : Ground state electron configuration The most stable, lowest energy electron arrangement of an atom
Each element has a ground-state electron configuration
Three Rules for Electron Arrangement : Three Rules for Electron Arrangement Aufbau Principle
Pauli Exclusion Principle
Hund’s Rule
Aufbau Principle : Aufbau Principle Each electron occupies the lowest energy orbital available
In order to do this, you must learn the sequence of atomic orbitals from lowest to highest energy
Aufbau Diagram
Each box represents an orbital
Each arrow represents an electron
Only two arrows per box…
Only two electrons per orbital
Some important things to remember about Aufbau… : Some important things to remember about Aufbau… All orbitals related to an energy sublevel are of equal energy
All three 2p orbitals have the same energy
In a multi-electron atom, the energy sublevels within a principle energy level have different energies
All three 2p orbitals are of higher energy than the one 2s orbital
Slide 29 : In order of increasing energies, the sequence of energy sublevels within a principle energy level is s, p, d, f
Orbitals related to energy sublevels within one principle energy level can overlap orbitals related to energy sublevels within another principle level
Ex. An orbital related to the atoms 4s sublevel has a lower energy than the five orbitals related to 3d sublevel.
Pauli Exclusion Principle : Pauli Exclusion Principle States that a maximum on 2 electrons can occupy a single atomic orbital but only if the electrons have opposite spins Wolfgang Pauli
Austrian Physicist
Observed atoms in excited states
Slide 32 : Each electron has a spin
Kinda like a spinning top
It can only spin in one of 2 directions
In order for electrons to be together in an orbital, they must have opposite spins
Hund’s Rule : Hund’s Rule What kind of charge do electrons have?
Do they attract or repel each other?
So……..
Hund’s Rule states that single electrons with the same spin must occupy all each energy equal orbital before additional electrons with opposite spins can occupy the same orbital
2p orbitals : 2p orbitals