Structure of the Atom — Flashcards
Karnataka Board · Class 9 · Science
20 flashcards for Structure of the Atom (Karnataka Board Class 9 Science) to test yourself on key terms and facts.
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A plastic comb attracts small pieces of paper after combing dry hair. Why does this happen?
Answer
When the comb rubs against hair, electrons transfer between them, creating electric charges. The charged comb attracts neutral paper pieces because atoms contain charged particles (electrons and proto…
What are canal rays and who discovered them?
Answer
Canal rays are positively charged radiations discovered by E. Goldstein in 1886 in a gas discharge tube. These rays led to the discovery of protons - positively charged particles with mass approximate…
An atom has 6 protons and 6 electrons. Will it carry any charge?
Answer
No, the atom will be electrically neutral. Since the number of positive charges (protons = 6) equals the number of negative charges (electrons = 6), they balance each other out. Total charge = (+6) + …
What was Thomson's model of the atom and why was it called the 'plum pudding model'?
Answer
Thomson proposed that an atom is a positively charged sphere with electrons embedded in it, like currants in a Christmas pudding. The positive charge was spread throughout the sphere while electrons w…
In Rutherford's gold foil experiment, why did most alpha particles pass straight through?
Answer
Most alpha particles passed straight through because most of the atom is empty space. Only when alpha particles came very close to the tiny, dense nucleus were they deflected. This proved that the ato…
What happens when an alpha particle hits the nucleus of a gold atom directly?
Answer
When an alpha particle hits the nucleus directly, it gets deflected by 180° (bounces straight back). This happens because both the alpha particle and nucleus are positively charged, so they repel each…
Why was Rutherford's atomic model considered unstable according to classical physics?
Answer
According to classical physics, a charged particle (electron) moving in a circular orbit undergoes acceleration and should continuously radiate energy. This would cause the electron to spiral into the…
How did Bohr solve the problem of atomic stability?
Answer
Bohr proposed that electrons can only exist in certain fixed orbits (discrete energy levels) around the nucleus. While in these special orbits, electrons do not radiate energy, making the atom stable.
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Sources & Official References
- Karnataka SSLC — kseeb.kar.nic.in
- Dept of Pre-University Education, Karnataka
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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