Electron Configurations and Periodic Table

Overview

• Previous video covered electron configuration for Neon: 1s2 2s2 2p6.
• Used periodic table to deduce electron configurations.
• Current focus is on elements in the third period, beginning with Sodium.

Sodium (Na)

• Sodium has 11 electrons, one more than Neon.
• Electron Configuration: 1s2 2s2 2p6 3s1
  • First 10 electrons match Neon, 11th electron enters the 3rd shell.
• Explanation:
  • 3rd Shell (n=3): Contains 3s, 3p, and 3d orbitals.
  • Sodium's 11th electron occupies the 3s orbital.
• Noble Gas Notation: [Ne] 3s1

Aluminum (Al)

• Aluminum has 13 electrons.
• Electron Configuration: 1s2 2s2 2p6 3s2 3p1
  • Follows Neon configuration, adds electrons to 3s and 3p orbitals.
• Noble Gas Notation: [Ne] 3s2 3p1

Argon (Ar)

• Argon has a complete third shell.
• Electron Configuration: 1s2 2s2 2p6 3s2 3p6
• Noble Gas Notation: [Ne] 3s2 3p6

Potassium (K)

• Potassium is in the fourth period.
• Electron Configuration: 1s2 2s2 2p6 3s2 3p6 4s1
  • Electron enters the 4s orbital instead of the 3d orbital due to lower energy.
• Noble Gas Notation: [Ar] 4s1

Calcium (Ca)

• Electron Configuration: 1s2 2s2 2p6 3s2 3p6 4s2
  • Fills the 4s orbital with two electrons.
• Noble Gas Notation: [Ar] 4s2

Understanding Electron Configurations

• S Block: Elements such as Sodium and Calcium have configurations involving only s orbitals.
• D Block:
  • There are five d orbitals in the third energy level; each can hold 2 electrons.
  • D orbitals accommodate the next 10 elements after Calcium.

Gallium (Ga)

• Electron Configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p1
  • Involves filling 3d orbitals.
• Noble Gas Notation: [Ar] 4s2 3d10 4p1

Krypton (Kr)

• Electron Configuration: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
• Noble Gas Notation: [Ar] 3d10 4s2 4p6

Additional Notes

• Noble Gas Notation: Efficient way to write electron configurations using the previous noble gas.
• Hund's Rule: Important for understanding how electrons fill orbitals.
• Future Learning: Detailed exploration of d orbitals will be covered separately.

Summary

• This lecture covered electron configurations from Sodium to Krypton, highlighting the S and D blocks within the context of the periodic table.
• Noble gas notation simplifies the representation of electron configurations.
• Understanding orbital energies is key to determining electron placement.