Question

1. state two key purposes of john daltons atomic theory.
2. j.j. thomson conducted an experiment using a cathode ray tube. what did he observe that led to the discovery of the electron?
3. describe the basic setup of ernest rutherfords gold foil experiment.
4. what were the two main unexpected observations from rutherfords gold foil experiment?
5. briefly compare and contrast the key features of the atomic models proposed by john dalton and ernest rutherford.

Explanation:

1. Dalton's atomic theory aimed to explain matter composition and chemical reactions. It proposed atoms as indivisible building - blocks and that atoms of different elements combine in fixed ratios.
2. Thomson observed that cathode rays were deflected by electric and magnetic fields, indicating they were composed of charged particles, which led to the discovery of electrons.
3. Rutherford's gold foil experiment involved firing alpha - particles at a thin gold foil. A detector was placed around the foil to record the scattered alpha - particles.
4. The unexpected observations were that most alpha - particles passed straight through the foil, and a small fraction were deflected at large angles or even bounced back.
5. Dalton's model had atoms as solid, indivisible spheres. Rutherford's model had a small, dense, positively - charged nucleus with electrons orbiting around it. Dalton's model didn't account for sub - atomic structure, while Rutherford's did.

Answer:

1. To explain matter composition and chemical reactions.
2. Deflection of cathode rays by electric and magnetic fields.
3. Firing alpha - particles at a thin gold foil with a detector around it.
4. Most alpha - particles passed straight through; a small fraction were deflected at large angles or bounced back.
5. Dalton: solid, indivisible spheres; Rutherford: small, dense nucleus with orbiting electrons.