Electron Configuration How do you describe the electronic structure of an atom using Lewis dot structures, electron orbital diagrams and electron configuration notations?

Valence Electrons Electrons that are lost/gained or shared when forming bonds Electrons in the OUTERMOST shell of an atom Represented in the group number All elements want 8 Lets take a look…..

Lewis Dot structure 1st: determine the elements number of valence electrons 2nd: place dots around the symbol to represent the valence electrons Ex: You try: Aluminum Chlorine

Electrons Bohr: placed electrons in energy levels Energy levels aren’t perfect circles With in each energy level we can give a more specific location of the electron Kind of like a street address Electron configuration: the “exact” location of an electron at a given time

Energy levels Describes the likely position of electrons within the atom Max # electrons per energy level (shell) = 2(n2), n is energy level Each Energy level has the same number of sublevels (subshells)

So….. How many sublevels would you find in the 1st energy level? Names? How many sublevels would you find in the 2nd energy level? How many sublevels would you find in the 3rd energy level? How many sublevels would you find in the 4th energy level?

Orbitals Each sublevel is divided into specific number of ORBITALS Each orbital can hold a MAX of 2 electrons An orbital is represented by a line: 1s __

Summary NOTE: Must fill the NEXT energy levels “s” sublevel PRIOR to filling the CURRENT energy levels “d” sublevel You must know the following order of electron filling….. 1s22s22p63s23p64s23d104p65s24d10

Aufbau Principle energy levels must be filled from the lowest to the highest and you may not move on to the next level unless the previous level is full. The first example DOES NOT FOLLOW Aufbau because electrons have been placed in the 3rd energy level before the second was complete The second example is FOLLOWS Aufbau because the second energy level is full before electrons have been placed in the 3rd energy level.

Hund’s Rule When placing electrons in orbitals, place one electron in each orbital before doubling up Singly occupy before doubly occupying The ensures electrons are in order to arrive at the lowest energy configuration Wrong RIGHT

Pauli Exclusion Principle States that when electrons do share an orbital, they must be of different “spin.” Must put one UP arrow & one DOWN arrow in a doubly occupied orbital

Identify each error and corresponding rule

Configuration and the Periodic Table Remember: the period numbers refer to the energy levels, so you can write electron configuration like you read a book when looking at the periodic table.

Parts of electron Configuration 1 = energy level S = sublevel 2 = electron in the orbital 1s___ ___ = orbital 2 arrows = electron in the orbital

Lets Practice: H He Be N Na Al Ca Br

Notations: Short Hand Long hand Noble Gas configuration Ex. 1s22s22p63s2 Long hand Ex. 1s __ 2s __2p __ __ __ Noble Gas configuration Ex. [He] 2s22p4