Electrons: The Bohr Model, Orbitals, and Electron Configuration Unit 1 Notes

Electron Configuration THREE THINGS NEEDED: Energy Level Orbital Type Number of Electrons

ENERGY LEVELS

Draw a picture of the Bohr model List one pro and one con of the model

Bohr models Each orbit or energy level is symbolized with the letter n, this is called its principle quantum number

Energy Levels The period (row) in which the element is found in tells us the number of energy levels the atom will have

How many energy levels would the following atoms have? Can you draw them? Helium Argon Germanium Nitrogen

Energy Levels The atomic number of the element tells us the total number of electrons the atom will have Remember: Ions will have a different number of electrons due to their charge!

Maximum number of electrons Energy Levels The energy levels each have a maximum number of electrons they can hold

ORBITALS

Orbitals Each energy level is made up of different types of orbitals Orbitals are areas within an atom where electrons are most likely to be found

Quantum Model Erwin Schrödinger used calculus and quantum mechanics to analyze the electrons energy and make a density plot of where the electron will probably be based on their wave-like properties.

Quantum Model Schrödinger found four different recurring shapes when plotting electron density Each one of these shapes is called an orbital and has a corresponding letter

Quantum Model

s - Orbitals

p - Orbitals 3 types (sublevels)

d - Orbitals 5 types (sublevels)

f - Orbitals

ELECTRONS

Orbitals Each energy level is made up of different types of orbitals Each orbital sublevel can hold two electrons

p - Orbitals 3 types (sublevels) 2 e- 2 e- 2 e- 6 e- (full)

Electron Configuration How electrons are organized in the atom Three parts: Principal quantum number (energy level) Orbital type Number of electrons in orbital 3s2

Electron Configuration How electrons are organized in the atom Three parts: Principal quantum number (energy level) Orbital type Number of electrons in orbital 3s2

Electron Configuration How electrons are organized in the atom Three parts: Principal quantum number (energy level) Orbital type Number of electrons in orbital 3s2

Electron Configuration How electrons are organized in the atom Three parts: Principal quantum number (energy level) Orbital type Number of electrons in orbital 3s2

Electron Configuration and orbital filling diagrams How to fill up all the energy levels and their orbitals with electrons: 3 Rules

Rule 1: Aufbau’s Rule Electrons start filling with the lowest energy level and fill up from there: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p

Rule 1: Aufbau’s Rule

Rule 1: Aufbau’s Rule 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p

Rule 2: Hund’s Rule Each orbital is made up of its sublevels. One electron occupy must occupy each sublevel before electrons can pair up in a sublevel.

Rule 3: Pauli’s Exclusion Principle Paired electrons must have opposite spins (one spin UP, one spin DOWN)

PRACTICE: Draw the electron configuration and orbital filling diagram for oxygen.

Valence Electrons Valence electrons - The electrons in an atom that are involved in the formation of chemical bonds; These are in the outer energy level. All remaining electrons in the other energy levels are called the core electrons.

Valence Number The valence number coordinates to the number of valence electrons

How many electrons would the following atoms have? How many of these electrons are valence electrons? Helium Argon Germanium Nitrogen

BOHR MODELS Draw the electron configuration and orbital filling diagram for phosphorus.

Draw the Bohr Model for phosphorus. BOHR MODELS Draw the Bohr Model for phosphorus. STEPS to Drawing Bohr Models: 1) Draw the nucleus (p+ and no) 2) Determine the energy levels by period 3) Fill outer energy level first by the column (valence) number. 4) Fill from inside out until you reach the outer level. This should use all of the electrons.