BTEC Applied Science Unit One: Chemistry Electron Configuration

Overview

• Electrons in Atoms: Electrons revolve around an atom in energy levels called shells.
• Shells: Labeled as n = 1, 2, 3, etc.
• Subshells: Within shells, called s, p, d, f (focus on s, p, d).
• Orbitals: Each subshell contains orbitals. Each orbital can hold a maximum of two electrons.

Shells and Subshells

• N=1 Shell: Contains only an s subshell.
• N=2 Shell: Contains s and p subshells.
• N=3 Shell: Contains s, p, and d subshells.

Orbitals

• S Subshell: 1 orbital
• P Subshell: 3 orbitals
• D Subshell: 5 orbitals
• F Subshell: Implied to have more orbitals, beyond basic course requirements.

Electron Capacity

• First Shell: Holds 2 electrons (s orbital only).
• Second Shell: Holds 8 electrons (s and p orbitals: 2 + 6).
• Third Shell: Holds 18 electrons (s, p, and d orbitals: 2 + 6 + 10).

Example Configurations

Fluorine

• Electrons: 9
• Configuration: 1s² 2s² 2p⁵
• Filling Order: Fill lower energy levels first, with electrons spinning oppositely (up and down arrows).

Calcium

• Electrons: 20
• Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
• Filling Order: 4s subshell fills before 3d.

Magnesium Ion (Mg²⁺)

• Electrons: 10
• Configuration: 1s² 2s² 2p⁶
• Similar to: Neon

Practice

• Drawing Electron Configurations: Practice drawing electron configurations for the first 20 elements.
• Ions: Consider group numbers for ion charges (Group 1: +1, Group 2: +2, Group 7: -2, Group 0: Noble gases, typically do not form ions).

Tips

• Visualization: Electron configuration is akin to people choosing empty seats on a bus (fill up seats that are free).
• Practice Makes Perfect: Repeated practice will solidify understanding, especially useful for exams.

Reminder

• Group Terminology: Group 0 refers to inert gases; avoid confusion with "Group 8".