Calculating Protons, Neutrons, and Electrons in Atoms and Ions 🧪

Introduction

• Example: Sodium
• Periodic Table:
  • Atomic number = number of protons (smaller number)
  • Average atomic mass (larger number)
• Isotopes:
  • Sodium-23: Most abundant
  • Other isotopes: Sodium-22, Sodium-24
• Atomic number: Identity of the element
• Mass number: Can change for different isotopes

Key Formulas

• Protons: Equal to the atomic number
• Neutrons: Difference between mass number and atomic number
• Electrons:
  • For atoms: Equal to the atomic number
  • For ions: Atomic number minus the charge

Practical Examples

Sodium Example

• Atomic number: 11
• Mass number: 23
• Protons: 11
• Neutrons: 23 - 11 = 12
• Electrons: 11 (no charge)
  • For neutral atoms: Protons = Electrons

Aluminum Ion (Al³⁺) Example

• Atomic number: 13
• Mass number: 27
• Protons: 13
• Neutrons: 27 - 13 = 14
• Electrons: 13 - 3 = 10
  • Positive ions: More protons than electrons

Sulfide Ion (S²⁻) Example

• Atomic number: 16
• Mass number: 33
• Protons: 16
• Neutrons: 33 - 16 = 17
• Electrons: 16 - (-2) = 18
  • Negative ions: More electrons than protons

Silicon Example

• Given: Silicon-29
• Atomic number: 14 (from periodic table)
• Mass number: 29
• Protons: 14
• Neutrons: 29 - 14 = 15
• Electrons: 14 (no charge)

Challenge Problem

Cation with 4+ Charge, 26 Neutrons, and 18 Electrons

• Determine atomic number using: Electrons = Atomic number - Charge
• 18 = A - 4
• Atomic number (A): 22
  • Indicates element is Titanium (Ti)
• Mass number: Neutrons + Protons
  • 26 + 22 = 48

Conclusion

• Identify element by finding the number of protons and using periodic table
• Key takeaway: Understanding atomic structure and isotopes is crucial for these calculations