Unit 2: Atoms and Bonding 2.63 Bohr’s model, Quantum Mechanical model, electron configuration Textbook ch 6.5, 6.8, and 6.9

Big Idea 1: The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions. Students will be able to demonstrate understanding by laboratory investigation, analysis of data and creation of models. SWBAT: Draw an energy-level diagram for the orbitals in a many electron atom and describe how electrons populate the orbitals in the ground state of an atom, using the Pauli exclusion principle and Hund’s rule Draw an energy-level diagram for the orbitals in a many electron atom and describe how electrons populate the orbitals in the ground state of an atom, using the Pauli exclusion principle and Hund’s rule Use the periodic table to write condensed electron configurations and determine the number of unpaired electrons in an atom Use the periodic table to write condensed electron configurations and determine the number of unpaired electrons in an atom Learning Objectives :

Rutherford - Bohr Model Three subatomic particles Three subatomic particles Protons Protons Positively Charged Positively Charged Found in nucleus Found in nucleus Neutrons Neutrons Neutral Charge Neutral Charge Found in nucleus Found in nucleus Electrons Electrons Negatively Charged Negatively Charged Found in orbits/clouds around nucleus Found in orbits/clouds around nucleus Overall charge of atom = 0Overall charge of atom = 0 Bohr Model Of Nitrogen

Placing Electrons in Orbits (or energy level) Orbit #1 maximum 2 electrons Orbit #1 maximum 2 electrons Orbit #2 maximum 8 electrons Orbit #2 maximum 8 electrons Orbit #3 maximum 8 electrons Orbit #3 maximum 8 electrons Orbit #4 maximum 18 electrons Orbit #4 maximum 18 electrons Orbit #5 maximum 18 electrons Orbit #5 maximum 18 electrons Orbit #6 maximum 32 electrons Orbit #6 maximum 32 electrons Orbit #7 maximum 32 electrons Orbit #7 maximum 32 electrons Where in the periodic chart do you see the same pattern? Where in the periodic chart do you see the same pattern? # of elements in each row in periodic table 2, 8, 8, 18, 18, 32, and 32 To fill: Electrons always go in inner orbits first, then are filled outward as the inner orbits fill up To fill: Electrons always go in inner orbits first, then are filled outward as the inner orbits fill up

Placing Electrons in Orbits Example – Calcium atom: Example – Calcium atom: 20 electrons 20 electrons You try this one! You try this one!

6+ 20 p + 20 n 0 Example – Calcium atom: 20 electrons 2 in first orbit 8 in second orbit 8 in third orbit 2 in fourth orbit

Model of atom: So far our basic idea of the model has been the Rutherford-Bohr model (2-D) So far our basic idea of the model has been the Rutherford-Bohr model (2-D) It is great for simplistic models but we are now going to start to talk about a more updated model - Quantum Mechanical Model It is great for simplistic models but we are now going to start to talk about a more updated model - Quantum Mechanical Model

Electron Energy Level (Shell) Principle Quantum number Electron Energy Level (Shell)“n” is also known as the Principle Quantum number or Electron Energy Level (Shell) The energy levels are 1-7 The energy level ALSO equals the period # or row # from the periodic table.

Nucleus (+) Principle energy level sublevels # of orbitals in each sublevel n=1 n=2 n=3 n =4 s s,p s, p, d s, p, d, f 1 1,3 1,3,5 1,3,5,7 Principle Quantum number Electron Energy Level Shell Orbit The Principle Quantum number or Electron Energy Level or Shell or Orbit is further broken down. Sublevels Orbitals

Rule #1 Aufbau Principle Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule” “Lazy Tenant Rule”

RIGHT WRONG Rule #2 Hund’s Rule Within a sublevel, place one e - per orbital before pairing them. Within a sublevel, place one e - per orbital before pairing them. “Empty Bus Seat Rule” “Empty Bus Seat Rule”

Rule #3 Pauli Exclusion Principle- Wolfgang Pauli Each orbital can hold TWO electrons with opposite spins.

O 8e - Electron Orbital Diagram Electron Orbital Diagram Electron Configuration Notation 1s 2 2s 2 2p 4 1s 2s 2p

Electron Configuration Notation Shows the energy level number Shows the energy level number Shows the sublevel type Shows the sublevel type Shows how many electrons are in that orbital Shows how many electrons are in that orbital Example 1: Helium has 2 electrons, both in the first energy level and the s sublevel. We write the electron configuration as: 1s 2 1s 2 Pronounced: “one s two” 1 st energy level s sublevel 2 electrons

s block is 2 elements wide p block is 6 elements wide d block is 10 elements wide f block is 14 elements wide s, p, d, f Blocks laid out correctly: How do these numbers appear in the periodic chart?

© 1998 by Harcourt Brace & Company s p d (n-1) f (n-2) Periodic Patterns (see handout) n

See handout Order: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 6

Shorthand Configuration Shorthand Configuration S 16e - Valence Electrons (outer electrons) Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4 Noble Gas Notation (Short cut) Longhand Configuration Longhand Configuration

B. Periodic Patterns Shorthand Configuration Shorthand Configuration Core e - : Go up one row and over to the Noble Gas. Core e - : Go up one row and over to the Noble Gas. Valence e - (outer electrons): On the next row, fill in the # of e - in each sublevel. Valence e - (outer electrons): On the next row, fill in the # of e - in each sublevel.

[Ar]4s 2 3d 10 4p 2 C. Periodic Patterns Example - Germanium Example - Germanium

Full energy level Full energy level Full sublevel (s, p, d, f) Full sublevel (s, p, d, f) Half-full sublevel Half-full sublevel D. Stability

Terms Isoelectronic: Atoms/Ions that have the same electron configurations Core electrons: Electrons in the lower energy levels Valence electrons: Electrons in the outer energy level

References I modified the original PPTs to fit our needs in AP Chemistry. Our textbook: Brown, Lemay et all. AP edition chemistry, 13 th edition, 2015