Understanding Atoms and Their Structure

Basic Concepts

• Everything is made up of tiny particles known as atoms.
• A single cell can contain over 100 trillion atoms.

Atom Structure

• An atom consists of:
  • A nucleus at the center.
  • Electrons that orbit the nucleus in shells.
• The nucleus comprises:
  • Protons
  • Neutrons

Particle Properties

Mass

• Protons and Neutrons:
  • Both have a relative mass of 1.
• Electrons:
  • Much smaller mass, often considered as 0.

Charge

• Protons:
  • Positive charge (+1).
• Neutrons:
  • No charge (neutral).
• Electrons:
  • Negative charge (-1).

Key to Remember:

• Positive Protons
• Neutral Neutrons
• Negative Electrons

Size of Atoms

• Atom radius: approximately 0.1 nanometers.
• Most of the atom is empty space.
• The nucleus is 10,000 times smaller than the atom itself.

Ions

• Atoms can gain or lose electrons, resulting in charged particles called ions.
• Negative Ion: More electrons than protons (e.g., 3 protons and 4 electrons is a 1- negative ion).
• Positive Ion: More protons than electrons (e.g., 3 protons and 2 electrons is a 1+ positive ion).

Elements and the Periodic Table

• Each box in the periodic table represents a different type of atom, or element (e.g., Oxygen, Lithium).

Nuclear Symbols

• Elemental Symbol: One or two letters representing the element (e.g., O for Oxygen, Li for Lithium).
• Atomic Number: Number of protons (O has 8, Li has 3).
• Mass Number: Total number of neutrons and protons.
  • To find neutrons:
    • Mass Number - Atomic Number
  • Example:
    • Oxygen: 16 (mass number) - 8 (atomic number) = 8 neutrons.
    • Lithium: 7 (mass number) - 3 (atomic number) = 4 neutrons.

Summary

• Atoms are composed of protons, neutrons, and electrons.
• The number of protons determines the element type.
• Ions form when atoms gain or lose electrons, leading to an imbalance in charge.