Electron Configuration

Electron Configuration

Electrons as Waves Review Louis de Broglie (1924) Applied wave-particle theory to electrons ELECTRONS EXHIBIT WAVE PROPERTIES Louis de Broglie ~1924 QUANTIZED WAVELENGTHS 200 Fundamental mode 200 Second Harmonic or First Overtone 200 Standing Wave 150 150 150 100 100 100 50 50 50 0 0 0-50 - 50-50 -100-100 -100-150 -150-150 -200 0 50 100 150 200-200 0 50 100 150 200-200 0 50 100 150 200 Adapted from work by Christy Johannesson www.nisd.net/communicationsarts/pages/chem

An electron is both a particle and a wave, but not at the same time.

Rutherford s Atomic Model- Review Does not explain all properties about atoms.

Rutherford s Atomic Model- Review Does not explain chemical properties of elements. Ex. Why metals or compounds give off characteristic colors when heated in a flame.

Bohr Model- Review Bohr proposed that electrons are arranged in circular orbits around the nucleus.

Schrodinger- Review Developed a mathematical equation describing the behavior of an electron. Quantum mechanical model- shows how likely it is to find the electron in various locations.

Atomic Orbital Atomic orbital = a region of space in which there is a high probability of finding an electron. Each orbital holds up to 2 electrons and is denoted by a different letter. Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

Overall Shapes

Atomic Orbitals

Electrons cannot choose any orbital they wish. They are restricted to orbitals with only certain energies. Electrons can jump from one energy level to another, but they can never have orbitals with energies other than the allowed energy levels.

Energy Levels http://www.chem4kids.com/files/art/elem_pertable2.gif Quantum mechanics has a principal quantum number. It is represented by a little n. It represents the energy level similar to Bohr s model. n=1 describes the first energy Red Orange Yellow Green Blue Indigo Violet n=1 n=2 n=3 n=4 n=5 n=6 n=7 level n=2 describes the second energy level Etc. Each energy level represents a period or row on the periodic table. It s amazing how all this stuff just fits together.

The number of electrons allowed in each of the first four energy levels are shown here.

Sub-levels = Specific Atomic Orbitals Each energy level has 1 or more sub-levels which describe the specific atomic orbitals for that level. n = 1 has 1 sub-level (the s Blue = s block orbital) n = 2 has 2 sub-levels ( s and p ) n = 3 has 3 sub-levels ( s, p and d ) n = 4 has 4 sub-levels ( s, p, d and f ) There are 4 types of atomic orbitals: s, p, d and f Each of these sub-levels represent the blocks on the periodic table.

What is Electron Configuration? Distribution of electrons where they are found.

Electron Configuration This is like writing out addresses to keep track of e- and where they live. Energy level town Type of orbital street Electron spin - house

Why Electron Configuration? Electron configurations are important because they help us predict chemical behavior. Whether two elements will react or not. What kind of reaction will happen. How strong the reaction will be.

There are 4 types of orbitals and an orbital can only store 2 electrons. An s sub-shell is made up of 1 orbital. So, 1 s orbital can store 2 electrons. A p sub-shell is made up of 3 orbitals. So, 3 p orbitals can store 6 electrons. A d sub-shell is made up of 5 orbitals. So, 5 d orbitals can store 10 electrons. An f sub-shell is made up of 7 orbitals. So, 7 f orbitals can store 14 electrons. Smart puppies don t forget!

The element we are Element finding the electron symbol configuration for. # of electrons in the orbital # of or Electrons subshell He 1s 2 Energy level Orbital or subshell

Electron Configuration- Rules 3 important rules: 1. Aufbau Principle- Electrons occupy the orbitals of lowest energy first.

Electron Configuration- Rules 2. Pauli Exclusion principlean atomic orbital can fit at most 2 electrons. Two electrons must have opposite spins in each orbital

Electron Configuration- Rules 3. Hund s Rule - You have to put one e- in each orbital all with the same spin aligned before pairing electrons.

Hund s Rule in Action Empty Seat Rule

Sections of Periodic Table to Know s-block p-block d-block f-block

Practice Problems 1. H 2. He 3. Li 4. N 5. Cu 6. Kr 7. Ca 8. Rb 9. Cl 10.Ag

Exit Slip Instructions: Write out the electron configurations for the following atoms. 1. Be 2. Si 3. Fe 4. Rb

Electron Configuration 5.1-5.2 Day 2

Electron Configuration At times writing electron configurations for elements can get pretty lengthy. So There is a short hand way to writing electron configurations!!!

Electron Configurations- Short Hand Follow these simple rules: 1. Write the symbol of the noble gas before the element. 2. Then the rest of the electrons. Example: Aluminum - full configuration. 1s 2 2s 2 2p 6 3s 2 3p 1 Aluminum- short configuration: [Ne] 3s 2 3p 1

Practice Problems 1. Li 2. N 3. Cu 4. Kr 5. Ca 6. Rb 7. Cl 8. Ag

Exit Slip Instructions: Write out the electron configurations for the following atoms. Short hand. 1. Be 2. Si 3. Fe 4. Rb