Structure and Basics of Atoms

Key Concepts

• Atoms: Basic building blocks of matter, extremely small particles.

  • A single cell contains over 100 trillion.

• Atomic Structure:

  • Nucleus: Central part made up of protons and neutrons.
  • Electrons: Orbit around nucleus in shells.

Subatomic Particles

• Protons

  • Relative mass: 1
  • Charge: +1 (positive)

• Neutrons

  • Relative mass: 1
  • Charge: 0 (neutral)

• Electrons

  • Relative mass: ~0 (1/2000th of a proton)
  • Charge: -1 (negative)

Comparing Mass and Charge

• Same mass: Protons and neutrons
• Tiny mass: Electrons
• Charges:
  • Positive protons
  • Neutral neutrons
  • Negative electrons

Size of Atoms

• Dependent on element type
• General radius: ~0.1 nanometers
• Nucleus: 10,000 times smaller than an atom
• Mostly empty space: Electrons orbit nucleus
• Analogy: Solar system (central nucleus, orbiting electrons)

Atomic Neutrality and Ions

• Neutral Atoms: Equal number of protons and electrons
• Ions:
  • Formed by gaining or losing electrons
  • Negative ion: More electrons than protons
  • Positive ion: More protons than electrons
  • Charge notation: 1-negative, 2-negative, 1-plus, etc.

The Periodic Table and Elements

• Elements: Different types of atoms, represented in the periodic table
• Nuclear Symbols:
  • Element symbol: One or two letters (e.g., O for oxygen, Li for lithium)
  • Atomic number: Number of protons (and electrons)
  • Mass number: Total number of protons and neutrons

Examples

• Oxygen (O)

  • Atomic number: 8 (8 protons, 8 electrons)
  • Mass number: 16
  • Number of neutrons: 16 - 8 = 8

• Lithium (Li)

  • Atomic number: 3 (3 protons, 3 electrons)
  • Mass number: 7
  • Number of neutrons: 7 - 3 = 4

Important Points

• Protons determine the element
• Electrons equal protons in neutral atoms

Final Note

• Focus on mass and charge relationships of particles
• Atomic structure analogy for better understanding (solar system)