Atomic Structure and Elements

Introduction

• Everything, living or non-living, is made of small particles called atoms.
• Atoms are extremely small; a single cell may contain over 100 trillion atoms.

Structure of an Atom

• Basic Structure: Atoms consist of a central nucleus surrounded by orbiting electrons.
• Nucleus: Composed of protons and neutrons tightly packed together.
• Electrons: Orbit the nucleus in rings called shells and are constantly moving.

Particles in an Atom

• Protons:
  • Relative mass of 1.
  • Positive charge (+1).
  • Easy to remember as both proton and positive begin with 'p'.
• Neutrons:
  • Relative mass of 1.
  • Neutral charge (0).
  • Easy to remember as both neutron and neutral start the same way.
• Electrons:
  • Mass approximately 2000 times smaller than protons/neutrons.
  • Negative charge (-1).

Size and Composition

• Atoms have a radius of about 0.1 nanometers.
• Most of an atom is empty space, similar to the solar system structure.
• The nucleus is extremely small, about 10,000 times smaller than the atom itself.

Atomic Neutrality

• Atoms are neutral when they have an equal number of protons and electrons.
• Atoms can become charged (ions) by gaining or losing electrons:
  • Negative Ion: More electrons than protons, resulting in a negative charge.
  • Positive Ion: More protons than electrons, resulting in a positive charge.

Elements and the Periodic Table

• Each box in the periodic table represents a different type of atom, known as an element.
• Elemental Symbol: A one or two-letter symbol representing the element (e.g., O for Oxygen, Li for Lithium).

Important Numbers

• Atomic Number: Located at the bottom left of the element symbol; indicates the number of protons.
  • Determines the identity of the element.
  • The atomic number also equals the number of electrons in a neutral atom.
• Mass Number: Located at the top left of the element symbol; indicates the total number of protons and neutrons.
  • Neutrons = Mass Number - Atomic Number.

Examples

• Oxygen:
  • Atomic Number: 8
  • Mass Number: 16
  • Neutrons: 16 - 8 = 8
  • Electrons: 8
• Lithium:
  • Atomic Number: 3
  • Mass Number: 7
  • Neutrons: 7 - 3 = 4
  • Electrons: 3

Conclusion

• Understanding atomic structure is fundamental for identifying elements and their properties.
• The periodic table organizes these elements based on their atomic structure and properties.

Note

• More details on ions and the periodic table will be covered in subsequent videos.