2.06 Electron Configuration

Parts I and II

Part I: Bohr Model of the Atom

• How are electrons arranged in an atom?

• Bohr: Electrons in definite energy levels around the nucleus

• Explained Hydrogen but not comprehensive enough for other elements

Modern Theory for Electrons

• Modern Theory (also called the Quantum Mechanical Model or Electron Cloud Model): Electrons move in a “beehive” around the nucleus in a “cloud” of energy

• An _________ is a region of space where an electron is likely to be found

Shapes

• Different types of orbitals have sublevel shapes depending on how much energy there is:– s ___________– p ___________– d ___________– f ____________

Definitions

• Aufbau Principle--- electrons arrange to have the lowest energy so they fill from _______ energy to ________ energy

• Pauli Exclusion Principle---maximum of _______ electrons are in each orbital and they have ________ spins (shown by an up and down arrow in the orbital)

• Hund’s Rule---Fill ______ electron in each orbital all the way across then then go back to fill the second electrons if the electrons are available (think of filling a bus with one person in a seat first)

Orbitals

• Each orbital is shown as a box can hold a maximum of 2 electrons (one electron is represented with an “up” arrow and the other electron is represented with a “down” arrow)

s has 1 orbital = _____ electrons p has 3 orbitals = _____ electronsd has 5 orbitals = _____ electronsf has 7 orbitals = ___electrons

Periodic Table

Using the Periodic Table

Order of electrons filling the orbitals

Electron Diagram Example

Definitions

• Electron configuration is the written summary of the arrangement of _______ in an atom

• 1s22s22p63s23p3

• Noble gas configuration is the short cut that saves you time (yeah!) but you have to know all three. Go to the noble gas in the row ________ your element.

• [Ne] 3s23p3

Carbon Example

Valence Electrons

Part II: Titanium Example (review)

F orbitals

Exceptions Chromium (Cr) and Copper (Cu)

• Rule: Filled and ½ filled sublevels are stable• For these exceptions, one electron is

“promoted” to make the other sublevel more stable

Chromium Example (Exception)