chem lecture chap 2

Shell Capacity

• Definition of Shell Capacity: Refers to the maximum number of electrons that can be housed within each shell.
• Subshell: A smaller division within a shell that contains orbitals.

Subshell Capacities

Subshell S

• Number of Orbitals: 1
• Capacity of Electrons: 2
  • Each orbital can hold a maximum of 2 electrons.

Subshell P

• Number of Orbitals: 3
• Capacity of Electrons: 6
  • Calculation: 3 orbitals × 2 electrons per orbital = 6 electrons.

Subshell D

• Number of Orbitals: 5
• Capacity of Electrons: 10
  • Calculation: 5 orbitals × 2 electrons per orbital = 10 electrons.

Subshell F

• Number of Orbitals: 7
• Capacity of Electrons: 14
  • Calculation: 7 orbitals × 2 electrons per orbital = 14 electrons.

Summary of Subshell Capacities

• S: 1 orbital, 2 electrons.
• P: 3 orbitals, 6 electrons.
• D: 5 orbitals, 10 electrons.
• F: 7 orbitals, 14 electrons.

Hierarchical Structure of Electron Spaces

• Largest Space: Shell
• Medium Space: Subshell
• Smallest Space: Orbital
  • Analogy:
  • Shell = Buildings
  • Subshell = Stories in Buildings
  • Orbital = Rooms in Stories
  • Electrons = People in Rooms

Orbital Capacity

• Definition of Orbital Capacity: An orbital can hold a maximum of 2 electrons.
• Practical Comparison:
  • Example: University dorm room typically accommodates 2 students.
• Capacity is Maximum:
  • Example: If the capacity is 40, it is permissible to have less than 40 (e.g., 30).

Capacity Calculations for Shells

• Calculation Method:

  • Based on the number of subshells and electrons they can hold.

• Shell 1:

  • Subshells: 1 (S)
  • Total Electrons: 2 (from 1 orbital)

• Shell 2:

  • Subshells: 2 (S, P)
  • Electrons: 2 (S) + 6 (P) = 8 total.

• Shell 3:

  • Subshells: 3 (S, P, D)
  • Electrons: 2 (S) + 6 (P) + 10 (D) = 18 total.

• Shell 4:

  • Subshells: 4 (S, P, D, F)
  • Electrons: 2 (S) + 6 (P) + 10 (D) + 14 (F) = 32 total.

Shell Capacity General Formula

• General Formula for Electron Capacity:
  • ext{Capacity} = 2n^2
  • Where n is the shell level.
• Example Calculations:
  • Shell 1: 2(1^2) = 2
  • Shell 2: 2(2^2) = 8
  • Shell 3: 2(3^2) = 18
  • Shell 4: 2(4^2) = 32
• Limitation of Formula:
  • For Shells beyond 4, the capacity remains at 32.

Electron Configuration Overview

• Electron Configuration: Representation of where electrons are placed in the atom.
• Sodium (Na) Example:
  • Sodium has an atomic number of 11 (11 electrons).
• Electron Placement:
  • 1s: 2 electrons
  • 2s: 2 electrons
  • 2p: 6 electrons
  • 3s: 1 electron (total = 11)

Correlation between Periodic Table and Electron Configuration

• Shell Representation: Represented by the period number in the periodic table.
• Subshell Representation: Deployment of subshells in columns of the periodic table.
  • S block: First two columns
  • P block: Right of S block
  • D block: Transition metals (middle)
  • F block: Inner transition metals (two rows at the bottom)

Transitioning Between Shells and Subshells

• D Subshell:
  • Shell number for D: Period number - 1.
• F Subshell:
  • Shell number for F: Period number - 2.

Example: Chromium (Cr) Configuration

• Electron Count: Chromium has 24 electrons
• Electron Configuration Steps:
  • 1s: 2 electrons
  • 2s: 2 electrons
  • 2p: 6 electrons
  • 3s: 2 electrons
  • 3p: 6 electrons
  • 4s: 2 electrons
  • 3d: 4 electrons
• Final Configuration:
  • 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴

Conclusion

• Understanding Shells and Subshells:
  • Essential to grasping electron configurations and chemical behavior.
• Memorization of Capacities:
  • Distinction among different subshells is crucial in chemistry.