Post on 02-Jan-2016
Electron Orbitals and Electron Configurations
Part II (a)
From orbits to orbitals!
We are going to move from Bohr’s model into the Quantum model of the atom
We are moving closer to our current understanding of where electrons are located in the atom
33
Electron Cloud or OrbitalsElectron Cloud or Orbitals
Erwin SchrErwin Schrödinger used mathematics ödinger used mathematics to predict to predict probabilityprobability of finding an of finding an electron at a certain location in the electron at a certain location in the atomatomHe call the area of probability the electron cloud = the volume around the nucleus of an atom where its electrons are most likely found– I
Electron Cloud or OrbitalsElectron Cloud or Orbitals
We can’t be absolutely certain where any electron is at any time– But based on what science knows
presently, this is our very best guess
OrbitalOrbital = a region with a very high = a region with a very high probability of probability of finding finding the electron when the electron when it has a particular amount of energyit has a particular amount of energy
Electron Cloud or OrbitalsElectron Cloud or Orbitals
Think of the energy levels as the rungs on the ladder of the electron cloudJust like we can only stand on the rungs of a ladder and not between the rungs, the electron can be located only in certain energy levels within the atom– Lower energy levels are smaller and
located closer to the nucleus of the atom– Higher energy levels are larger and located
farther away from the nucleus
66
The Quantum-Mechanical ModelThe Quantum-Mechanical Model
Each Each energy level (or shell) energy level (or shell) contain the contain the same numbersame number of of subshells subshells or sublevels or sublevels as the energy levelas the energy level
The The subshellssubshells are represented as a are represented as a letterletter
– s, p, d, fs, p, d, f
Each subshell has Each subshell has orbitalsorbitals with a with a particular shape.particular shape.
77
Shells & SubshellsShells & Subshells
88
The Quantum-The Quantum-Mechanical ModelMechanical Model
Energy Level # of subshells Orbital shape
1 1 s
2 2 s and p
3 3 s, p, and d
Apartment Complex Analogy
Think of an atom like an apartment complex
The energy level or shell is the floor
The subshells are the type of apartment– s = suite d = deluxe– p = penthouse f = flat
The orbitals have different occupancies based on their shape
1010
Probability Maps & Orbital ShapeProbability Maps & Orbital Shapess orbitalsorbitals are spherical and are spherical and
have 1 orbitalhave 1 orbital
1111
Probability Maps & Orbital ShapeProbability Maps & Orbital Shapepp orbitalsorbitals look like dumb bells and look like dumb bells and
have 3 orbitalshave 3 orbitals
Probability Maps & Orbital Shape Probability Maps & Orbital Shape dd orbitals orbitals have 5 orbitalshave 5 orbitals
Probability Maps & Orbital ShapeProbability Maps & Orbital Shapef Orbitals have 7 orbitals
13
Atomic Orbitals
Watch the video (14:28)
http://www.youtube.com/watch?v=Ewf7RlVNBSA
Stop and answer questions about Atomic Orbitals
Electron Orbital Activity Lab
There are funny rules on how to fill the apartment complex or atom
Work with a partner to complete the electron configuration lab, but be sure
to follow these rules…
Apartment Rules
Rule A:From the Bottom Up: Rooms must be filled from the ground floor up. Fill the one room on the first floor before starting to put new tenants on the second floor. Then fill the s room before the p rooms. At higher floors the order might change a bit.
Apartment Rules
Rule B:Singles First: the owner of the building
wants to have the tenants spread out as much as possible. For that reason singles are placed in rooms before couples. If couples must be placed into a room then all of the other rooms on that floor must already have a single in them.
Apartment Rules
Rule C:
Opposite Gender Only: When two people are placed in a room they must be of opposite genders. No men may room together and no women may room together. This is an arbitrary rule on the part of the owners: in a just world we wouldn’t have to follow it. But quantum mechanics has nothing to do with justice.
Ions
Ions are atoms that have either lost or gained electrons
Remember electrons are negative, so how many protons and how many electrons would Cl -1 have?
Electron Lab
Now work with a partner to complete the Electron Orbital Activity Lab
What did we learn from the Lab?
Bohr part II (b)
Rule A: The Aufbau Principle
• Place electrons in the energy shells and orbitals in order of energy, from low energy to higher energy
– i.e. Electrons are Lazy!
– s → p → d → f
• All orbitals related to an energy level are of equal energy.
– i.e. The three 2p orbitals are the same energy level.
Rule B: Hund’s Rule
• When filling orbitals that have the same energy, place one electron in each before completing pairs
– i.e. Electrons are unfriendly! • Why? Electrons, being unfriendly, fill up
the empty orbitals before sharing orbitals. This is similar to seats on a bus – on a bus, you sit alone, rather than with a stranger, if there is an option.
Rule C: Pauli Exclusion Principle
A maximum of two electrons may occupy a single orbital, but only if the electrons have opposite spins.
– Spin -- Electrons have an associated “spin,” either one way or the other, like a top.
– These spins are called “spin up” and “spin down.”
Big take aways from the Lab
Exceptions to filling order are copper, chromium and some others
Most stable are completely filled shells
Next most stable are half-filled shells
An atom may borrow an electron from next s shell to half fill a lower energy level.
Take aways from the Lab
Did you notice something funny about the order of the energy levels or orbitals?
Energy levels Energy levels don’t don’t always go in always go in order!order!
Relative Energy Levels
Take aways from the Lab
Occupanies: Did you notice how many electrons could occupy each type of room?
Suites (s orbitals) could hold 2
Penthouse (p orbitals) could hold 6
Deluxe (d orbitals) could hold 10
Flats (f orbitals) could hold 14
Orbital Occupancies
Subshell Name Number of Orbitals
Max number of electrons
s- subshell 1 (sphere) 1 X 2 = 2
p – subshells 3 (dumbbells) 3 x 2 = 6
d – subshells 5 5 x 2 = 10
f – subshells 7 7 x 2 = 14
3030
Writing electron configurations
Electron configurationElectron configuration = = distribution of electrons into the distribution of electrons into the various energy shells and various energy shells and subshells in an atom in its subshells in an atom in its ground ground statestate
Electron Configurations
Electron configuration is address information for electrons
The most stable arrangement is called the ground-state electron configuration.
This is the configuration where all of the electrons in an atom reside in the lowest energy levels possible.
Electron Configurations
2p4
Energy LevelEnergy LevelSubshellSubshell
Number of Number of electrons in electrons in the subshellthe subshell
1s1s22 2s 2s22 2p 2p66 3s 3s22 3p 3p66 4s 4s22 3d 3d1010 4p 4p66 5s 5s22 4d 4d1010 5p 5p66 6s6s22 4f 4f1414…… etc.etc.
Tro's Introductory Chemistry, Chapter 9Tro's Introductory Chemistry, Chapter 9 3333
Electron ConfigurationsElectron Configurations
Nitrogen:Nitrogen: 1s 1s222s2s222p2p33
(atomic number = 7)(atomic number = 7)
energy levelenergy level orbitalorbital
how many electronsin that orbital
What about ions?
What did you notice about ions?
When writing electron configuration for ions (when an element loses or gains electrons to become more stable), do it exactly the same way for the ion’s number of electrons
Writing Electron Configurations
Wouldn’t it be nice if we could write electron configuration without doing the orbital diagrams?
Well, we can! But we need to be careful because the energy levels do not always go in order!
We can use the diagonal rule to help us!
Diagonal Ruless
s 3p 3ds 3p 3d
s 2ps 2p
s 4p 4d 4fs 4p 4d 4f
s 5p 5d 5f 5g?s 5p 5d 5f 5g?
s 6p 6d 6f 6g? 6h?s 6p 6d 6f 6g? 6h?
s 7p 7d 7f 7g? 7h? 7i?s 7p 7d 7f 7g? 7h? 7i?
11
22
33
44
55
66
77
By this point, we are past By this point, we are past the current periodic table the current periodic table so we can stop.so we can stop.
Writing Electron Configurations
Steps for the diagonal rule:Steps for the diagonal rule:Write the energy levels Write the energy levels top to bottomtop to bottom..Write the orbitals in s, p, d, f order. Write the orbitals in s, p, d, f order. Write the same number of orbitals as Write the same number of orbitals as the energy level.the energy level.Draw Draw diagonal linesdiagonal lines from the top right from the top right to the bottom left.to the bottom left.To get the correct order, To get the correct order, follow the arrows!follow the arrows!
Diagonal Rule
Now try it yourself on the blank side of the diagonal rule sheet
Doing this will be #1 on your next quiz!
Practice Using the Diagonal Rule
Work on writing the electron configurations for the 10 elements in the packet