4. both democritus and dalton proposed that matter consists of atoms. explain how their approaches to reaching the same conclusion differed.
5. describe the experiment that led to the discovery of the electron.
6. describe rutherford’s gold foil experiment. what did this experiment tell us about the structure of the atom?
7. what are the 3 subatomic particles? describe the differences between them in their masses, charges, and place within the atom.
8. since all atoms have negatively charged electrons, shouldn’t every atom have a negative charge? explain.

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### Question 5: Describe the experiment that led to the discovery of the electron.
# Brief Explanations:
J.J. Thomson conducted the cathode - ray tube experiment. A cathode - ray tube has a cathode (negative electrode) and an anode (positive electrode) in a vacuum - sealed tube. When a high voltage was applied, a ray (cathode ray) was emitted from the cathode. Thomson observed that these rays were deflected by electric and magnetic fields. The direction of deflection showed that the rays were composed of negatively charged particles. He also calculated the charge - to - mass ratio ($\frac{e}{m}$) of these particles, which were later named electrons.
# Answer:
J.J. Thomson's cathode - ray tube experiment: A high voltage was applied across electrodes in a vacuum tube. The emitted cathode rays (deflected by electric/magnetic fields, showing negative charge) led to electron discovery, with $\boldsymbol{\frac{e}{m}}$ calculated.

### Question 6: Describe Rutherford’s gold foil experiment. What did this experiment tell us about the structure of the atom?
# Brief Explanations:
- **Experiment Description**: Rutherford directed a beam of alpha ($\alpha$) particles (positively charged, from radioactive decay) at a thin gold foil. A fluorescent screen around the foil detected the scattered $\alpha$ - particles.
- **Results and Atomic Structure Insight**: Most $\alpha$ - particles passed through the foil (atom mostly empty space). Some were deflected at small angles, and a few (about 1 in 8000) were deflected at large angles (even back towards the source). This showed a small, dense, positively charged nucleus at the center of the atom (the large - angle deflections were due to $\alpha$ - particles hitting this nucleus), with electrons orbiting around it in the empty space.
# Answer:
- **Experiment**: $\alpha$ - particles bombarded thin gold foil; screen detected scattering.
- **Atomic Structure**: Atom has a small, dense, positive nucleus (most space empty, electrons orbit), from $\alpha$ - particle scattering (most pass, few large - angle deflections).

### Question 7: What are the 3 subatomic particles? Describe the differences between them in their masses, charges, and place within the atom.
# Brief Explanations:
The three subatomic particles are protons, neutrons, and electrons.
- **Protons**: Mass $\approx 1.67	imes10^{-27}	ext{ kg}$ (or 1 atomic mass unit, amu), charge $+1e$ ($e = 1.6	imes10^{-19}	ext{ C}$), located in the nucleus.
- **Neutrons**: Mass $\approx 1.67	imes10^{-27}	ext{ kg}$ (1 amu), charge $0$, located in the nucleus.
- **Electrons**: Mass $\approx 9.11	imes10^{-31}	ext{ kg}$ (negligible compared to proton/neutron), charge $- 1e$, located in electron cloud (around the nucleus).
# Answer:
- **Subatomic Particles**: Protons, Neutrons, Electrons.
- **Differences**:
    - Protons: $m\approx1.67	imes10^{-27}	ext{ kg}$, $+1e$, in nucleus.
    - Neutrons: $m\approx1.67	imes10^{-27}	ext{ kg}$, $0$, in nucleus.
    - Electrons: $m\approx9.11	imes10^{-31}	ext{ kg}$, $-1e$, in electron cloud.

### Question 8: Since all atoms have negatively charged electrons, shouldn’t every atom have a negative charge? Explain.
# Brief Explanations:
Atoms have protons (positive charge) in the nucleus and electrons (negative charge) in the electron cloud. In a neutral atom, the number of protons (positive charge) is equal to the number of electrons (negative charge). So the positive and negative charges cancel out, resulting in a net charge of zero for the atom. Only when an atom gains or loses electrons (forming an ion) does it have a net positive or negative charge.
# Answer:
No. Atoms have protons (positive) in nucleus. In neutral atoms, number of protons = number of electrons, so charges cancel (net charge 0). Ions (charged) form when electrons are gained/lost.

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Question 5: Describe the experiment that led to the discovery of the electron.

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Question 6: Describe Rutherford’s gold foil experiment. What did this experiment tell us about the structure of the atom?