Structure of the Atom
Punjab Board · Class 9 · Science
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See them allWhat are canal rays and who discovered them?
Answer
Canal rays are positively charged radiations discovered by E. Goldstein in 1886 during gas discharge experiments. These rays passed through holes (canals) in the cathode and ultimately led to the disc…
Compare electrons and protons in terms of charge and mass.
Answer
Electrons: Negative charge (-1), mass negligible relative to protons, represented as 'e'. Protons: Positive charge (+1), mass taken as 1 unit, represented as 'p'. A proton is approximately 2000 times …
An atom contains 1 electron and 1 proton. Will it carry any charge?
Answer
No, it will be electrically neutral. The positive charge of the proton (+1) and the negative charge of the electron (-1) cancel each other out, making the net charge zero. This is the hydrogen atom (H…
Describe Thomson's Model of the Atom with an analogy.
Answer
Thomson proposed that atoms consist of a positively charged sphere with electrons embedded in it, like currants (dried fruits) in a Christmas pudding or seeds in a watermelon. The model showed that ne…
Why was Thomson's Model of the atom considered inadequate?
Answer
Thomson's model could not explain the results of experiments conducted by other scientists, particularly Rutherford's alpha-particle scattering experiment. The model failed to account for the highly c…
What were alpha-particles used for in Rutherford's experiment and why gold foil?
Answer
Alpha-particles are doubly-charged helium ions with mass 4u and high energy, making them ideal projectiles for investigating atomic structure. Gold foil was chosen because it could be made extremely t…
State the three main observations from Rutherford's alpha-particle scattering experiment.
Answer
1. Most alpha-particles passed straight through the gold foil without deflection. 2. Some alpha-particles were deflected by small angles. 3. Surprisingly, about 1 in 12,000 alpha-particles rebounded b…
Use the barbed-wire fence analogy to explain Rutherford's results.
Answer
If a child throws stones at a barbed-wire fence, most stones pass through gaps without hitting anything (like alpha-particles passing through the atom). If stones hit the fence, they may be deflected …
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