Electron Configurations

Bohr Model Issues While the Bohr Model correctly positions electrons into energy levels, the true locations of electrons aren’t shown. Instead of electrons following a set circular path around the nucleus, they are randomly found in regions of space we call orbitals.

Quantum Mechanical Model This model uses probability functions to calculate an area of space that takes a specific shape around the nucleus. The orbital is the region where these electrons are found approximately 90% of the time.

Quantum Numbers Principal Quantum Numbers: Show relative sizes and energy of orbital sublevels n = 1 (1st level) n = 2 (2nd level) n = 3 (3rd level) n = 4 (4th level)

Identifying n What is the principal energy level for the outermost electron in the following element?

Identifying n What is the principal energy level for the outermost electron in the following element?

Identifying n What is the principal energy level for the outermost electron in the following element?

Orbital Basics Different orbitals have different shapes and sizes. Additional shapes are possible for orbitals in the same energy sublevel.

Energy Sublevels There is a pattern to the location where the electrons are found on the periodic table.

Orbital Sublevels In which orbital sublevel would you find the final electron for the atom below? A)4s B)3s C)3p D)2p

Orbital Sublevels In which orbital sublevel would you find the final electron for the atom below? A)2s B)3s C)3p D)4p

Orbital Sublevels In which orbital sublevel would you find the final electron for the atom below? A)4d B)4s C)3d D)4p

Orbital Sublevels In which orbital sublevel would you find the final electron for the atom below? A)5f B)5d C)7f D)7s

Energy Sublevels The type of orbital being filled determines the number of orbitals available in a sublevel. s: only 1 orbital per sublevel p: 3 orbitals per sublevel d: 5 orbitals per sublevel f: 7 orbitals per sublevel Once an orbital sublevel is filled, the next electron is placed in the next sublevel up.

Electron Filling Principles 1) The Aufbau Principle: an electron will occupy the lowest energy position possible (Think Rule)

Electron Filling Principles 2) Pauli Exclusion Principle: A single orbital can hold at most 2 electrons (with opposite spin). 3) Hund’s Rule: An electron will fill an unoccupied orbital in an energy sublevel before sharing an orbital with another electron.

Orbital Diagrams Orbital diagrams use the electron filling principles to show the number of orbitals that are filled, partially filled, or empty. Arrows represent electrons with up or down spin in an orbital.

Orbital Diagram Practice True or False: the correct orbital diagram for sulfur is shown below

Orbital Diagram Practice True or False: the correct orbital diagram for vanadium is shown below

Orbital Diagram Practice True or False: the correct orbital diagram for copper is shown below

An Easier Way… You’ll notice that if you show every electron being filled, larger atoms would take a very long time to write. We have electron configurations to help simplify that process. Electron configurations abbreviate an orbital sublevel with the sublevel- type-number notation. 2p42p42p42p4

Electron Configurations Full electron configurations show all orbital sublevels in the order the electrons are filled up. Shortened (noble gas) configurations start with the last noble gas electron filled and then the remaining electrons. 1s 2 2s 2 2p 6 3s 2 3p 3 [Ne]3s 2 3p 4

Electron Configuration Practice Which of the following is the correct electron configuration for oxygen? A)1s 2 2p 6 B)1s 2 2s 2 2p 4 C)2p 4

Electron Configuration Practice Which of the following is the correct electron configuration for potassium? A)1s 2 2s 2 2p 6 3s 1 A)1s 2 2s 2 2p 6 3s 1 B)1s 2 2s 2 2p 6 3s 2 3p 7 C)1s 2 2s 2 2p 6 3s 2 3p 6 4s 1

Electron Configuration Practice Which of the following is the correct electron configuration for molybdenum? A)1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 4 A)1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 4 B)1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 4d 10 4p 6 5s 2 5d 4 C)1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 5 C)1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 5

Short Configuration Practice Which of the following is the correct short- form electron configuration for silicon? A)[Ne] 3p 2 A)[Ne] 3p 2 B)[Ne] 3s 2 3p 2 C)[Ar] 3s 2 3p 2

Short Configuration Practice Which of the following is the correct short- form electron configuration for chromium? A)[Ar] 4s 2 3d 4 B)[Kr] 4s 2 3d 4 C)[Ar] 4s 1 3d 5

Short Configuration Practice Which of the following is the correct short- form electron configuration for lead? A)[Xe] 6s 2 4f 14 5d 10 6p 2 A)[Xe] 6s 2 4f 14 5d 10 6p 2 B)[Xe] 6s 2 5d 10 6p 2 B)[Xe] 6s 2 5d 10 6p 2 C)[Xe] 6s 2 6p 2 C)[Xe] 6s 2 6p 2

Lewis Symbols Lewis symbols show the element symbol surrounded by only electrons that fill the outer s & p orbitals. LiCAl Cl

Lewis Symbol Practice Draw the Lewis Symbol for each of the following atoms: BaN PbAg