8.1 – 8.3 Student Notes

II. Electron Configurations and Periodicity

A. Electronic Structure of Atoms

1. Electron Configurations and Orbital Diagrams

a. Electron configuration –

b. Orbital diagram –

2. Pauli Exclusion Principle

a. Def -

b. Pauli exclusion principle:

B. Building-Up Principle and the Periodic Table

1. Background

a. Ground state –

b. Excited state –

2. Building-Up Principle (Aufbau Principle)

a. Def –

b. 1s, 2s, 2p, 3s, 3p, 4s, 4p, 5s, 4d, 5s, 6s, 4f, 5d, 6p, 7s, 5f

Lowest

c. Shows why the noble gases are so stable

3. Electron Configuration and the Periodic Table

a. Noble-gas core –

b. Pseudo-noble-gas core –

c. Valence electron –

4. Exceptions to the Building-Up Principle

a. Chromium

Expect [Ar] 3d⁴4s²

Actual

b. Copper

Expect [Ar] 3d⁹ 4s²

Actual

C. Writing Electron Configurations Using the Periodic Table

1. Determining the Configuration of an Atom Using the Building-Up Principle

Use the building-up principle to obtain the configuration for the ground state of the gallium atom (Z = 31). Give the configuration in complete form (do not abbreviate for the core). What is the valence-shell configuration?

2. Determining the Configuration of an Atom Using the Period and Group Numbers

What are the configurations for the outer electrons of

a. Tellurium

b. Nickel