Modern Atomic Model Sometimes called: Charge Cloud Model Wave Mechanical Model Quantum Theory Theory created to help describe spectral line signatures of multi-electron elements Crash Course: History of Atomic Theory (9:45) https://www.youtube.com/watch?v=thnDxFdkzZs

How is it Different from the Planetary Model? We can’t tell exactly where an electron is!! Heisenberg’s Uncertainty Principle: We can’t know exact location and momentum of an electron at the same time.

Electrons exist in “orbital clouds” Denser the cloud region the higher the probability of finding an electron there. Can’t tell exactly where an electron is, but can tell region of higher probability of finding it.

Excited Atoms and Charge Cloud Excited electrons shift to probability regions further from the nucleus

Comparison to Bohr’s Electron Model Charge Cloud = area of highest probability of finding electron, but can’t know exact location Bohr Model = electrons in fixed orbit like planet around the sun at fixed distance from nucleus

STOP HERE HONORS ONLY MATERIAL LIES BEYOND

Extra Videos Quantum Mechanics and the Bohr Model (6 minutes) http://www.youtube.com/watch?v=-YYBCNQnYNM **Developing Modern Atomic Theory (6min) Rutherford to Bohr to the Modern Model http://youtu.be/45KGS1Ro-sc The Uncertainty Principle (6min) Honors Probability & Chance of Finding an e- and Orbital Shapes http://www.youtube.com/watch?v=Fw6dI7cguCg

How are Electrons Organized? Energy Levels Sublevels Orbitals Spin The Electron Hotel

Energy Levels (1-7) Energy Levels 1 2 3 4 5 6 7 Electrons exist at different distances from the nucleus. Energy Levels 1 2 3 4 5 6 7 Lowest energy Highest energy Closest to nucleus Farthest from Nucleus

Sublevels (s, p, d, f) Energy levels have certain number of sublevels. Energy Level Sublevels Possible 1 s 2 s, p 3 s, p, d 4 s, p, d, f 5 s, p, d, f, (g) 6 s, p, d, f, (g, h) 7 s, p, d, f, (g, h, i) Theoretical sublevels

Energy of Sublevels Sublevels have different levels of energy. s p d f Lowest energy Highest energy

Orbitals in Sublevels Sublevels contain different numbers of orbitals. Maximum 2 electrons can exist in an orbital. Sublevel # of Orbitals Max e- in Sublevel s 1 2 e- p 3 6 e- d 5 10 e- f 7 14 e-

Aufbau Diagram Shows: Follow the “diagonal rule” order of electron filling order of electron energy Follow the “diagonal rule”

Writing Electron Configurations Let’s write some electron configurations! Ex: Magnesium Follow the diagonal rule

Overlap Some sublevels “overlap” Results in certain sublevels having higher energy than others Ex: 3d has higher energy than 4s

Electron Configurations for Atoms http://employees.oneonta.edu/viningwj/sims/atomic_electron_configurations_s1.html Extremely Corny Song About Electron Configurations http://www.youtube.com/watch?v=Vb6kAxwSWgU&safe=active

Electron Spin Electrons in an orbital spin in opposite directions Pauli Exclusion Principle: In order for two electrons to occupy the same orbital, they must have opposite spins. Otherwise they create a magnetic field!

Orbital Diagrams Show electrons in individual orbitals s = 1 orbital, p = 3 orbitals, d = 5 orbitals, f = 7 orbitals “Hund’s Rule for Orbital Filling” When filling orbitals in a sublevel, place one electron in each orbital before adding the second.

Paramagnetic vs. Diamagnetic Diamagnetic: only paired electrons in orbitals Paramagnetic: at least one orbital with an unpaired electron. Diamagnetic atoms repel magnetic fields. The unpaired electrons of paramagnetic atoms realign in response to external magnetic fields and are therefore attracted. Paramagnets do not retain magnetization in the absence of a magnetic field, because thermal motion randomizes the spin orientations. http://employees.oneonta.edu/viningwj/sims/electron_configurations_t2.html

Shapes of Orbitals Orbitals come in different shapes and sizes. Region of highest probability of finding an electron. Orbitals Shape & Energy & Spectral Line http://www.youtube.com/watch?v=fKYso97eJs4

Probability cloud has a spherical shape s Orbital Probability cloud has a spherical shape

p Orbitals (px, py, pz) “Dumbell” shape Three p orbitals can exist, on the x, y, z axis in space

Clouds and Probability

Five possible d orbitals exist

Seven possible f orbitals exist

Valence Electrons Usually found in the s and p sublevels of highest occupied energy level. How many valence electrons? Draw a Lewis Dot Diagram of this element. 1s22s22p63s23p64s23d104p2

Kernel 1s22s22p63s23p3 All electrons except the valence How many kernel electrons? How many valence? 1s22s22p63s23p3

Excited vs. Ground State Electron configuration you would normally write by following the order of filling Lowest to highest energy. Excited State: one or more electrons have jumped up to a higher energy level. Ex: 1s22s22p63s23p54s23d104p3

Atom vs. Ion Configurations Ions: atoms that have gained or lost electrons. Figure out how many electrons the ion has then write configuration. Ex: 20Ca+2 has 18 electrons 1s22s22p63s23p6 = 18 electrons DONE! Electron Configurations for Ions http://employees.oneonta.edu/viningwj/sims/atomic_electron_configurations_s2.html

Isoelectronic Species Atoms and ions that have the same number of electrons. Ex: Ar, K+1, Ca+2, P-3, O-2, Cl-1 All have 18 electrons!

Impossible Configurations Break the rules. Ex: 1s22s22p63s22d103p64s23d104p2 Ex: 1s22s32p63s23p6

s, p, d, f, “Blocks” Indicates what sublevel is being filled last in the atom

Some Exceptions to Orbital Filling (HONORS) When d and f sublevels get filled near the end of a configuration we sometimes see exceptions. It is more stable for the orbitals of the d and f sublevels to be half filled or filled completely than to be one shy. Electrons from the sublevel below get “promoted” up to make the atom more stable Ex: Copper

Crash Course Chemistry: The Electron (13 minutes) http://www.youtube.com/watch?v=rcKilE9CdaA

Quantum Numbers (Honors) Set of 4 numbers that help to describe most probable location of each of an atom’s electrons.

Principal Quantum Number: (n) describes principle energy level electron is in values n = 1, 2, 3, ...7 n=2 can describe the 8 electrons in 2nd energy level

Azimuthal Quantum Number: (ℓ) Describes sublevel electron is in (s, p, d, f) Values of (ℓ)  range from: 0 to (n-1) Ex: If n=4 ℓ can be 0, 1, 2, 3 (representing s, p, d, f sublevels) If n=2 ℓ can be 0, 1 (representing s, p sublevels) n = 2 ℓ = 1 means the electrons in 2”p” n = 3 ℓ = 2 means the electrons in 3 “d”

Magnetic Quantum Number: (mℓ) Describes the orbital the electron is in on sublevel Relates to it’s general orientation in space Values from (-ℓ….0….+ℓ) **note the middle orbital is ZERO Number of possible m values within a sublevel is = to the number of orbitals within a sublevel Ex: ℓ= 1 (p sublevel), mℓ= -1, 0, +1 (representing px, py, pz orbitals) Ex: n= 3, ℓ= 2, mℓ= -1 (describes the 2 electrons in the 2nd orbital in 3d)

Spin Quantum Number: (ms ) Values of +1/2 or -1/2 (arrow up or arrow down) 1st electron in orbital is “clockwise” = +1/2 2nd electron in orbital is “counterclockwise” = -1/2 Ex: n=2, ℓ = 1, mℓ = +1, ms = -1/2 Represents 2p6 electron