Drill – 10/30

1. What is an orbital? Is an electron always within it?

2. What is the electron configuration for carbon (C)?

3. What is the electron configuration for gallium (Ga)?

Drill – 11/4

• Write the electron configuration for Helium and identify the components of an electron configuration.

Drill – 11/8

Write the electron configurations for:

1. Tin (Sn)

2. Mercury (Hg)

• Electron arrangement can be written in one of 3 ways:

• (1) Electron configuration

• (2) Orbital diagram

• (3) Noble-gas notation

Orbital Notation

• Arrows indicate electrons.

• Boxes, circles or lines represent each orbital

3 Rules for Electron Arrangement

• Aufbau Principle

– Electrons always start filling at the lowest energy level.

– Within each energy level, the s sublevel fills first, then p, then d, then f.

3 Rules for Electron Arrangement

Pauli Exclusion Principle

–A maximum of 2 electrons can be in one orbital. They must have opposite spins.

3 Rules for Electron Arrangement

Hund’s Rule

–Electrons fill each orbital in a sublevel before they start pairing up.

p orbitals

Orbital Diagram

1s 2s 2px 2py 2pz

Oxygen

8 electrons

1s22s22p4

Exceptions to the Aufbau Principle

Write the configurations for:

• Chromium (Cr)

• Copper (Cu)

Actual Configurations for Cr and Cu

• Cr: 1s22s22p63s23p64s13d5

• Cu: 1s22s22p63s23p64s13d10

WHY??

• Draw the correct orbital diagrams for each Cr and Cu.

WHY??

• Having a half-filled or completely-filled d subshell gives the element a special stability

• d4 & d9 column will have exceptions every time!!

Noble Gas Notation• Shorthand e- configuration

– e- configurations of noble gases can be written using bracketed symbols

ex: Ne

1s22s22p6 = [Ne]– Write the bracketed symbol for the noble gas

that precedes the element (period above it) and then continue filling orbitals with remaining electrons.

P 15 1s22s22p63s23p3 [Ne]3s23p3

Element # of e- e- configurationNobel gas notation

Ar 18 1s22s22p63s23p6

Ca 20 1s22s22p63s23p64s2 [Ar]4s2

Ne 10 1s22s22p6 [He]2s22p6

Br 35 1s22s22p63s23p64s2

3d104p5

[Ar]4s23d104p5

[Ne]3s23p6