chemistry notes

Chapter 7 : The structure of atoms.

  • Thales:

    • Looked around him and used what he saw to explain the world, believing that the world formed from water.

    • "Whales with a T" concept.

  • Anaximenes:

    • A student of Thales who disagreed, proposing that everything is made of air, as everything is surrounded by it.

  • Democritus:

    • Suggested that if you cut something into smaller pieces until it can no longer be divided, you will reach an indivisible particle called an atom.

    • Proposed that atoms of different sizes and shapes exist and can join together to make various substances.

  • Aristotle:

    • Introduced the idea that everything is composed of four fundamental elements: earth, water, air, and fire, which can transform into one another.

  • Antoine Lavoisier:

    • Investigated changes during chemical reactions, formulating the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.

  • John Dalton:

    • Proposed the atomic theory stating that all matter is made of atoms, that atoms of a given element are identical in mass and properties, and that compounds are formed by the combination of different types of atoms.

    • Studied gases:

    • 1st gas = 1 carbon + 1 oxygen

    • 2nd gas = 1 carbon + 2 oxygen

    • Noted that one theory was incorrect: he claimed atoms were indivisible, but we now know about protons, neutrons, and electrons.

  • J.J. Thompson (Joseph J. Thompson):

    • Discovered the first subatomic particles, identifying negative particles called electrons.

    • Proposed the plum pudding theory where negatively charged toppings exist in a positive pudding base.

    • Noted that electrons were the first subatomic particles discovered.

  • Rutherford:

    • Discovered the nucleus through the gold foil experiment, demonstrating that atoms consist of a small, dense positively charged core surrounded by electrons.

    • Named the particles inside the nucleus as protons.

  • James Chadwick:

    • Discovered the neutron, providing a more complete picture of atomic structure by revealing another fundamental particle in the nucleus.

  • Ernest Rutherford:

    • Discovered three types of radiation: alpha particles, beta particles, and gamma rays.

  • Isotopes:

    • Atoms of an element that have different numbers of neutrons are called isotopes.