Understanding Electron Configuration and Orbitals in Atomic Structure, Study Guides, Projects, Research of Chemistry

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Electron Configuration

(Section 5.2)

Dr. Walker

Objectives

• To determine the electron configuration of any

of the first 38 elements of the periodic table

• To determine the identity of an element from

its electron configuration

• To complete an orbital diagram using arrows

to represent electrons

Where are Electrons?

• Orbitals are areas within shells where the electrons are located - These orbitals may have different shapes - There may be different numbers of orbitals within a shell
• We know the electron is somewhere in the orbital, but we can’t know exactly where it is or how fast it is moving - Heisenberg’s Uncertainty Principle
• Each orbital can hold two electrons (Pauli Exclusion Principle)

Learning Check

• What are orbitals? A place where electrons

can be found

• Where are orbitals? Outside the nucleus

• How many electrons reside in each orbital? 2

Types of Orbitals (subshells)

• S orbitals – 1 orbital per shell – holds ___ electrons total
• P orbitals – 3 orbitals per shell – holds ___ electrons total
• D orbitals – 5 orbitals per shell – holds ___ electrons total
• F orbitals – 7 orbitals per shell – holds ___ electrons total

Actual Electron Configurations

• Total electrons = atomic number

• Electrons are added one at a time to the

lowest energy levels first (Aufbau principle)

• Fill energy levels with electrons until you run

out

• A superscript states how many electrons are in

each level

Order of Orbitals

• Low Energy to High Energy (# of electrons)
  • 1s (2)
  • 2s (2)
  • 2p (6)
  • 3s (2)
  • 3p (6)
  • 4s (2)
  • 3d (10)
  • 4 p (6)
  • 5s (2)
  • Continues for the whole periodic table
  • You’re expected to know through here

Another option

• Draw the orbitals in this format, use diagonal

lines to determine order of orbitals to fill

Actual Electron Configurations

• Total electrons = atomic number

• Fill energy levels with electrons until you run

out

• A superscript states how many electrons are in

each level

• Hydrogen – 1s^1 – 1 electron total
• Helium – 1s^2 – 2 electrons total
• Lithium – 1s^2 2s^1 – 3 electrons total
• Beryllium – 1s^2 2s^2 – 4 electrons total

Actual Electron Configurations

• Bigger Elements

• Fill the energy levels until you run out of electrons
• Oxygen
  • 1s^2 2s^2 2p^4
• Sodium
  • 1s^2 2s^2 2p^6 3s^1
• Titanium
  • 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^2

Practice

• Potassium