Unit 2: Atoms and BondingUnit 2: Atoms and Bonding

2.63 Bohr’s model, 2.63 Bohr’s model, Quantum Mechanical Quantum Mechanical

model, electron model, electron configurationconfigurationTextbook ch 6.5, 6.8, and Textbook ch 6.5, 6.8, and

6.96.9

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:SWBAT:Draw an energy-level diagram for the Draw an energy-level diagram for the orbitals in a many electron atom and orbitals in a many electron atom and describe how electrons populate the orbitals describe how electrons populate the orbitals in the ground state of an atom, using the in the ground state of an atom, using the Pauli exclusion principle and Hund’s rulePauli exclusion principle and Hund’s ruleUse the periodic table to write condensed Use the periodic table to write condensed electron configurations and determine the electron configurations and determine the number of unpaired electrons in an atomnumber of unpaired electrons in an atom

Learning Objectives:

Rutherford - Bohr Rutherford - Bohr ModelModel

Three subatomic particlesThree subatomic particles ProtonsProtons

Positively ChargedPositively Charged Found in nucleusFound in nucleus

NeutronsNeutrons Neutral ChargeNeutral Charge Found in nucleusFound in nucleus

ElectronsElectrons Negatively ChargedNegatively Charged Found in orbits/clouds around Found in orbits/clouds around

nucleusnucleus• Overall charge of atom = 0Overall charge of atom = 0

Bohr ModelOf Nitrogen

Placing Electrons in Orbits (or energy level)

Orbit #1 maximum Orbit #1 maximum 22 electrons electrons Orbit #2 maximum Orbit #2 maximum 88 electrons electrons Orbit #3 maximum Orbit #3 maximum 88 electrons electrons Orbit #4 maximum Orbit #4 maximum 1818 electrons electrons Orbit #5 maximum Orbit #5 maximum 1818 electrons electrons Orbit #6 maximum Orbit #6 maximum 3232 electrons electrons Orbit #7 maximum Orbit #7 maximum 32 32 electronselectrons

Where in the periodic chart do you see the Where in the periodic chart do you see the same pattern?same pattern?

# of elements in each row in periodic table 2, 8, 8, 18, 18, 32, and 32

To fill:To fill: Electrons always go in inner orbits first, Electrons always go in inner orbits first, then are filled outward as the inner orbits fill upthen are filled outward as the inner orbits fill up

Placing Electrons in OrbitsPlacing Electrons in Orbits Example – Calcium atom:Example – Calcium atom:

20 electrons20 electrons You try this one!You try this one!

6+20 p+

20 n0

Example – Calcium atom:Example – Calcium atom:20 electrons20 electrons2 in first orbit2 in first orbit8 in second orbit8 in second orbit8 in third orbit8 in third orbit2 in fourth orbit2 in fourth orbit

Model of atom: Model of atom: So far our basic idea of the model has So far our basic idea of the model has

been the Rutherford-Bohr model (2-D)been the Rutherford-Bohr model (2-D)

It is great for simplistic models but we It is great for simplistic models but we are now going to start to talk about a are now going to start to talk about a more updated model - more updated model - Quantum Quantum Mechanical ModelMechanical Model

Electron Energy Level Electron Energy Level (Shell)(Shell)

•“n” is also known as the Principle Principle Quantum number Quantum number or Electron Energy Level Electron Energy Level (Shell)(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 orbitalsin eachsublevel

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

The Principle Quantum number Principle Quantum number or Electron Energy Level Electron Energy Level or Shell Shell or OrbitOrbit is further broken down.

•Sublevels •Orbitals

Rule #1 Rule #1 Aufbau Aufbau PrinciplePrincipleElectrons fill the Electrons fill the

lowest energy lowest energy orbitals first.orbitals first. ““Lazy Tenant Lazy Tenant

Rule”Rule”

RIGHTWRONG

Rule #2 Rule #2 Hund’s RuleHund’s Rule Within a sublevel, place one eWithin a sublevel, place one e-- per per

orbital before pairing them.orbital before pairing them. ““Empty Bus Seat Rule”Empty Bus Seat Rule”

Rule #3Rule #3 Pauli Pauli Exclusion Exclusion Principle-Principle-

Wolfgang Pauli

Each orbital can hold TWO electrons with opposite spins.

O 8e-

Electron Orbital DiagramElectron Orbital Diagram

• Electron Configuration Notation

1s2 2s2 2p4

1s 2s 2p

Electron Configuration Electron Configuration NotationNotation

Shows the energy level Shows the energy level numbernumber Shows the Shows the sublevel typesublevel type Shows how many Shows how many electronselectrons are in that orbital are in that orbitalExample 1:Example 1:Helium has Helium has 22 electrons, both in the first energy electrons, both in the first energy

level and the s sublevel.level and the s sublevel.We write the electron configuration as:We write the electron configuration as:

1s1s22

Pronounced: “one s two”Pronounced: “one s two”1st 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 How do these numbers appear in the periodic chart?in the periodic chart?

© 1998 by Harcourt Brace & Company

s p

d (n-1)

f (n-2)

1234567

67

Periodic Patterns Periodic Patterns (see handout)(see handout)

n

See handout

Order: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6

Shorthand ConfigurationShorthand Configuration

S 16e-

Valence Electrons(outer electrons)

Core Electrons

S 16e- [Ne] 3s2 3p4

1s2 2s2 2p6 3s2 3p4

Noble Gas NotationNoble Gas Notation(Short cut)(Short cut)

Longhand ConfigurationLonghand Configuration

1

2

3

4

5

6

7

B. Periodic PatternsB. Periodic Patterns Shorthand ConfigurationShorthand Configuration

Core eCore e--:: Go up one row and over to the Go up one row and over to the Noble Gas.Noble Gas.

Valence eValence e- - (outer electrons):(outer electrons): On the On the next row, fill in the # of enext row, fill in the # of e-- in each in each sublevel.sublevel.

[Ar] 4s2 3d10 4p2

C. Periodic PatternsC. Periodic Patterns Example - Example - GermaniumGermanium

Full energy levelFull energy level

1 2 3 4 5 6 7

Full sublevel (s, p, d, f)Full sublevel (s, p, d, f)

Half-full sublevelHalf-full sublevel

D. StabilityD. Stability

TermsIsoelectronic:

Atoms/Ions that have the same electron configurations

Core electrons:Electrons in the lower energy levels

Valence electrons:Electrons in the outer energy level

ReferencesReferenceswww.sciencegeek.net/Chemistry

I modified the original PPTs to fit our needs in AP Chemistry.

Our textbook: Brown, Lemay et all. AP edition chemistry, 13th edition, 2015