Electron Configuration

Quantum mechanical model review The quantum mechanical model : Protons and neutrons are still in the dense nucleus Electrons are confined to certain energy levels, but do not have an exact position or an orbit within the atom Electrons are in the electron cloud, which is the location they are likely to be found in 90% of the time. The darker the area the more likely the electrons will be there.

Energy Levels Electrons are limited to specific energy levels Primary Energy levels are represented by numbers n = 1 is the first energy level n = 2 is the second energy level, etc. The higher the energy level the more energy it has Within each energy level are energy sublevels (s, p, d, f) The s- sublevel has the least energy and the f has the most energy

Orbitals Within each sublevel are orbitals Atomic orbitals: The areas around the nucleus where it is most likely to find an electron Each orbital holds a maximum of 2 electrons

Sublevels & their Orbitals Type of Sublevel Shape # of Orbitals Max # of Electrons sSphere12 pDumbbell36 dCloverleaf510 fVaries714 Each sublevel can hold less than the maximum number of electrons

Orbital shapes

Different energy levels contain different sublevels Primary Energy Level Sublevel (Orbital) Types Total # of Orbitals Maximum # of Electrons 1s12 2s, p4 (1 + 3)8 3s, p, d9 ( )18 4s, p, d, f1632 5s, p, d, f1632 6s, p, d918 7s, p48

To Review In the atom there are energy levels ( n = 1, 2, 3, 4) In the energy levels are Sublevels (s, p, d, f) In the Sublevels there are orbitals – each orbital holds up to 2 electrons!!! S = 1 orbital P = 3 orbitals D = 5 orbitalsF = 7 orbitals

How many orbitals are in the following sublevels? 1. 3p 2. 2s 3. 4p 4. 3d 5. 4f

Electron Configuration The ways in which electrons are arranged around the nuclei of atoms A way to represent the number of electrons an atom has and the energy of those electrons In an atom, electrons and the nucleus interact to make the most stable arrangement possible using the least amount of energy Electron Configuration is not how atoms are formed- just how the electrons are arranged

3 rules tell us how to find the electron configuration of atoms: 1. Aufbau Principle Electrons enter orbitals of lowest energy first – starting with 1s

3 rules tell us how to find the electron configuration of atoms: 2. Pauli Exclusion Principle An atomic orbital can have at the most two electrons These electrons must have opposite spins, use arrows (↑↓) to indicate direction of spin

3 rules tell us how to find the electron configuration of atoms: 3. Hund’s rule When electrons occupy orbitals of equal energy each orbital fills with one electron at a time with parallel spins Then second electrons fills with opposite spin

With your table, answer the following questions 1. What are the four energy sublevels? 2. How many orbitals does each sublevel have? 3. How many electrons can an orbital hold? 4. How many total electrons can each sublevel hold? 5. What does the electron configuration tell you about the electrons in an atom? 6. What are the three rules that tell us how to find the electron configuration?

Aufbau Diagrams

Diagonal Rule: Orbitals fill up in a diagonal pattern

Examples: How many electrons does Aluminum have? How many electrons does Calcium have? Write the electron configuration for each element using the diagonal rule

With your table, write the electron configuration for… Cobalt Barium Bromine Phosphorus

HW for Monday Write the electron configurations for… Lithium, Oxygen, Magnesium, Chlorine, Nickel

Exceptions to the Diagonal Rule Copper and Chromium These TWO are exceptions to the diagonal rule when writing the electron configuration. They only fill 4s 1 before moving on to 3d This is because having at 1 electron in 4s and at least 1 electron in each 3d orbital is more stable than partially filled sublevels.

More Electron Configuration Practice Ca, Cu, Rb, I, Fe, As, Tc, Cr, Si and W

CHAPTER 5 BOOK ASSIGNMENT Pages , 33, 34, 36, 37, 38, 41, 44, 56, 60, 61, & 77 Due Thursday!