Structure of Atom

Antoine Lavoisier: Assisted by his wife Marie Anne, who made sketches of new equipment and translated scientific works for him.

Sketches: Created illustrations of experimental setups.
Translations: Helped Antoine access international scientific literature.

Proust's Experiments: Weighed chemicals to find consistent elemental proportions.
- Example: Copper carbonate decomposition yielded fixed ratios: 5 parts copper, 4 parts oxygen, 1 part carbon.
Law of Definite Proportions: Elements in a compound always combine in specific proportions, regardless of sample size.

John Dalton: Built on Lavoisier and Proust’s work.
- Observed gas combinations and developed concepts around atoms.
Key Postulates of Dalton's Theory:
- All matter is composed of atoms.
- Atoms are indivisible and indestructible.
- Atoms of the same element have identical masses and properties.
- Atoms of different elements have different masses.
- Atoms combine to form compounds in simple whole number ratios.

Studied atomic weights and hypothesized structure based on hydrogen as a fundamental unit.
Idea proved incorrect but spurred interest in atomic structure.

Discovery of Electrons: Utilized cathode ray tubes to identify particles smaller than hydrogen atoms (electrons).
Plum Pudding Model: Proposed that atoms consist of negatively charged electrons distributed in a positively charged substance (analogous to plum pudding).

Background: Studied under J.J. Thomson and investigated radiation with Paul Villard.
Experiment Setup: Fired alpha particles at a thin gold sheet to determine atomic structure.
- Predicted all particles would pass through if Thomson’s model were correct.
- Observed that some particles were deflected, indicating a nucleus in atoms.
Findings:
- Most alpha particles pass through, few were deflected; suggested a large amount of empty space in atoms with a dense, positively charged nucleus.

Proposed a new model where the nucleus is positively charged and surrounded by electrons in a larger, mostly empty space.
Identification of Protons: He named these positively charged particles protons, establishing the foundation for an atomic nucleus.

Rutherford hypothesized neutral particles in the nucleus, leading to James Chadwick’s discovery of neutrons in 1932.
Properties of Neutrons: Similar mass to protons but without an electric charge.
Charged Particles in Atoms:
- Protons (positive) and electrons (negative) create electrostatic forces that hold the atom together.

Limitations of Traditional Microscopes: Atoms are invisible to light microscopes due to their size.
Electron Microscopes: Developed to visualize atomic position within materials, albeit without detailed images of individual atoms.

Instrumental in the establishment of modern chemistry.
His wife, Marie Anne, contributed by making sketches of experimental setups and translating scientific works, enhancing Lavoisier's access to international literature.

Known for the Law of Definite Proportions based on weighing chemicals.
Found that compounds, like copper carbonate, always yield specific ratios of elements regardless of sample size.

Built on Lavoisier's and Proust's findings, formulating Dalton's Atomic Theory.
Key postulates: matter is made of indivisible atoms, atoms of the same element are identical, and compounds form in simple whole-number ratios.

Studied atomic weights and proposed that hydrogen is a fundamental unit of atomic structure, inspiring further exploration in atomic theory.

Discovered electrons using cathode ray tubes.
Proposed the Plum Pudding Model where electrons exist in a positively charged substance.

Conducted the Gold Foil Experiment, which revealed the atomic nucleus.
Proposed that most of an atom is empty space, with a dense, positively charged nucleus at its core.

Confirmed the existence of neutrons in 1932, completing understanding of the atomic nucleus.
Neutrons have a similar mass to protons but are electrically neutral.