Chemistry- Unit 3 Section II - Chapter 7 (7.6-7.8, 7.11) Quantum Mechanics
Atomic Review What subatomic particles do you get to play with? Protons Neutrons Electrons NO! It would change the element Don t Care - isotopes: only mass is different What we play with in chemistry
Bohr Model of the Atom electrons must circle the nucleus of an atom in certain paths Developed the concept of Energy Levels
Bohr Model of the Atom The model correctly fits the quantized energy levels of the hydrogen atom and postulates only certain allowed circular orbits for the electron Bohr s model is incorrect. This model only works for hydrogen Electrons do not move around the nucleus in circular orbits
Quantum (definition from Webster s) 1) quantity, amount 2) any of the very small increments or parcels into which many forms of energy are subdivided Quantum Theory -describes mathematically the wave properties of electrons and other very small particles *electrons were determined to have a dual waveparticle nature *uses two principles
Heisenberg uncertainty principle it is impossible to determine simultaneously both the position and velocity of an electron or any other particle Schrodinger Wave Equation treats electrons as waves around the nucleus Together these two principles determine the probability of finding electrons We do not know the detailed pathway of an electron
Orbital three-dimensional region around the nucleus that indicates the probable location of an electron To describe orbitals, we use.. Quantum Numbers specify the properties of atomic orbitals and the properties of electrons in orbitals there are 4 quantum numbers
Quantum Numbers Principal quantum number (n) size and energy of the orbital the main energy level occupied by the electron positive integers ranges from 1 to 7 equal to the period
Quantum Numbers Angular momentum quantum number (l or l) shape of atomic orbitals sometimes called a subshell Orbitals possible is equal to n Values of l are all integers less than l = n-1
Quantum Numbers Angular momentum quantum number (l or l) l subshell 0 s 1 p 2 d 3 f
Quantum Numbers Angular momentum quantum number (l or l)
Concept Check For principal quantum level n = 3, determine the number of allowed subshells (different values of l), and give the designation of each. # of allowed subshells = 3 l = 0 l = 1 l = 2 3s 3p 3d
Quantum Numbers Magnetic quantum number (m l ) orientation of the orbital in space relative to the other orbitals around the nucleus m l = ±l each subshell has a specific shape s subshell has 1 orbital one shape p subshell has 3 orbitals three shapes d subshell has 5 orbitals five shapes f subshell has 7 orbitals seven shapes Assign each family magnetic quantum number then repeat if needed You do NOT need to know the shapes
Electron spin quantum number (m s ) an orbital can hold only two electrons, and they must have opposite spins can be -½ or +½ Each electron must be distinguishable (different) from all others Start with the negative spin first
Quantum Numbers for the First Four Levels of Orbitals in the Hydrogen Atom
1s Orbital
Two Representations of the Hydrogen 1s, 2s, and 3s Orbitals
2p x Orbital
2p y Orbital
2p z Orbital
The Boundary Surface Representations of All Three 2p Orbitals
3d x2 -y Orbital 2
3d xy Orbital
3d xz Orbital
3d yz Orbital
3d z 2 Orbital
The Boundary Surfaces of All of the 3d Orbitals
Representation of the 4f Orbitals in Terms of Their Boundary Surfaces
Concept Check For l = 2, determine the magnetic quantum numbers (m l ) and the number of orbitals. magnetic quantum numbers = 2, 1, 0, 1, 2 number of orbitals = 5
Identify the four quantum number for the following elements: Element n l m l m s Lithium 2 0 0 -½ Bromine 4 1 0 +½ Silver 5 2 1 +½ Uranium 7 3-1 -½
Concept Check Identify the four quantum number for the following elements: Element n l m l m s Platinum 6 2 0 +½ Silicon 3 1 0 -½ Chlorine 3 1 0 +½ Radium 7 0 0 +½
Concept Check Identify the four quantum number for the following elements: Element n l m l m s Potassium 4 0 0 -½ Iron 4 2-2 +½ Arsenic 4 1 1 -½ Tungsten 6 2 1 -½
Electron Configurations the arrangement of electrons in an atom based on 3 rules Aufbau principle electrons occupy the lowest energy level they can Pauli exclusion principle in a given atom, no two electrons can have the same set of four quantum numbers
Electron Configurations Hund s Rule the lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate (same energy) orbitals orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron all electrons in singularly occupied orbitals must have the same spin
Orbital Energies
Orbital Energies
The Orbitals Being Filled for Elements in Various Parts of the Periodic Table
Electron Configuration Notation The order that electrons fill orbitals 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 6
Electron Configuration Notation What is the electron configuration for oxygen? 1s 2 2s 2 2p 4 What is the electron configuration for bromine? 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5
Electron Configuration Notation Instead of using the Periodic Table, you can make this chart to write electron configurations.
Electron Configuration Notation What is the electron configuration for Strontium? 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 What is the electron configuration for Erbium (Er)? 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 12 Review page 315 and 316 in book
Noble Gas Configuration Notation You can also use Noble Gases to show electron configurations since they have a fulfilled Octet Rule To do this, go backwards from your element to the closest Noble Gas and list it in brackets [ ] Starting from that point, list the electron configuration to your element It is really the same thing; it just shortens the configuration up. Don t use a Noble Gas Configuration unless asked to do so.
Noble Gas Configuration Notation What is the Noble Gas configuration for Chlorine? [Ne] 3s 2 3p 5 What is the Noble Gas configuration for Einsteinium (Es)? [Rn] 7s 2 5f 11
Orbital Diagram A notation that shows how many electrons an atom has in each of its occupied electron orbitals. Always draw up arrows (-½ spin) first Oxygen: 1s 2 2s 2 2p 4 Oxygen: 1s 2s 2p
Orbital Diagram Draw an orbital diagram for sulfur. Sulfur: 1s 2 2s 2 2p 6 3s 2 3p 4 3s 3p 2s 2p 1s
Concept Check Determine the expected electron configurations for each of the following. a) S 1s 2 2s 2 2p 6 3s 2 3p 4 b) Ba 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 c) Eu 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 7
Concept Check Determine the expected Noble Gas configurations for each of the following. a) S [Ne]3s 2 3p 4 b) Sr [Kr]5s 2 c) Au [Xe]6s 2 4f 14 5d 9
Concept Check Draw an Orbital Diagram for Aluminum. 3s 3p 2s 2p 1s
Valence Electrons The electrons in the outermost principal quantum level of an atom 1s 2 2s 2 2p 6 (valence electrons = 8) The elements in the same group on the periodic table have the same valence electron configuration Only going to be responsible for Main Group elements Range is from 1 to 8
Valence Electrons Chlorine 1s 2 2s 2 2p 6 3s 2 3p 5 [Ne] 3s 2 3p 5 7 valence electrons The number of valence electrons is equal to the group number minus 10 (unless it is a single digit, then it is the number of valence electrons)
Concept Check Determine the valence electrons for the following elements: a) S b) Sr c) B 6 2 3
Unit 3 Homework Set #2 pg 332: #67, 68, 70, 75, 76, 77, 79, 84, 89, 92, 132 (11)