Electron Configuration

Electron Configuration

An address for electron's location.

Multiple Choice

Review: How many electrons can each orbital hold?

• 2 electrons only

• it depends on the orbital shape

• 6 electrons

• 4 electrons

The Orbitals

• s - sphere- only one orbital

• p- dumbbell- three orbitals

• d- four petals- five orbitals

• f- six petals- seven orbitals

Multiple Choice

How many electrons can the p sublevel hold?

• 2

• 6

• 10

• 14

Orbital Blocks

on Periodic Table

The 'blocks' represent the sublevels of each level.

Notice that the s block has two columns representing its two max electrons.

The p block has six columns, the d block has ten, and the f block has fourteen.

One way to think of it is to move He into the S block.

Poll

Is it easier to identify the 's block' with Helium over Beryllium or where it belongs over Neon?

• Easier over Beryllium

• Easier over Neon

• It doesn't make a difference

There are 3 Principles/Rules to Electron Configuration

• Aufbau Principle (buidling up)

• Hund's Rule

• Pauli Exclusion Principle

Aufbau Principle

Lower levels fill first

One sublevel must be full before starting another

Aufbau Principle Exceptions

• d and f blocks appear to fill out of order!

• d block has a higher repulsion force than s or p, and will push electrons into the higher s orbital as it fills. (d blocks written as one shell down)

• f blocks fill in gaps in very large elements. The repulsion forces decrease the more the block fills, resulting in some interesting electron configuration. (f blocks written as two shells down)

Note numbering on d and f blocks.

Multiple Choice

Which sublevel fills first s, p, d or f in any level?

• s

• p

• d

• f

Multiple Choice

Based on aufbau arrow diagrams and the layout of the periodic table, which fills first?

• 3d

• 4s

aufbau arrows

Electron Configuration Formula

• Number of shell (energy level)

• Letter of orbital sublevel

• Number (superscript) of electrons in sublevel

• Example: 1s² 2s² 2p³ is for Nitrogen

Note numbering on d and f blocks.

Fill in the Blank

Let's practice: Write the electron configuration for Sodium (element 11)

Note numbering on d and f blocks.

Fill in the Blank

Write the electron configuration for Argon (element 18)

Note numbering on d and f blocks.

Fill in the Blank

Write the electron configuration for Titanium (element 22)

Hund's Rule

• All orbitals in a sublevel are singly occupied before any are doubly occupied.

• All singly occupied orbitals have the same spin. (to maximize spin)

Hund's Rule

Analogy: think of it like seats on a bus. Strangers will spread out before sitting next to someone else.

Multiple Choice

Which of these is Hund's Rule violated in?

• 1

• 2

• 3

• 4

Multiple Select

Which of these is Hund's Rule violated in?

• a

• b

• c

• d

Pauli Exclusion Principle

• An orbital can have a maximum of two electrons. Those electrons must have an opposite spin!

• (no two electrons can have the same four electronic quantum numbers. shell, orbital shape, magnetic pole position, and spin.)

Pauli Exclusion Principle

spin arrows point in opposite direction in each orbital.

Multiple Choice

Which of these does NOT violate the Pauli Exclusion Principle?

• a

• b

• c

• d

Lets put it all together

• Fill lowest energy level first. (exceptions in d and f sublevels)

• Fill sublevels completely before moving on to next. (exceptions made in f sublevels)

• In sublevels, orbitals fill singly before any fill doubly.

• All singly filled orbitals have same spin.

• Electrons in doubly filled orbitals have opposite spins.

aufbau arrows

Energy Ladder

Poll

Which chart is easiest for you to use?

• Periodic Table

• Aufbau Arrows

• Energy Ladder

• Not sure; I'm lost

Poll

What if anything is giving you trouble?

• Energy level numbers

• sublevel/orbital letters (s,p,d,f)

• number of electrons in sublevel

• Hund's or Pauli's rules (arrows in sublevels)

• none of these