Structure of the Atom — Flashcards
Gujarat Board · Class 9 · Science
25 flashcards for Structure of the Atom (Gujarat Board Class 9 Science) to test yourself on key terms and facts.
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What are subatomic particles? Name the three main subatomic particles found in an atom.
Answer
Subatomic particles are tiny particles that make up atoms. The three main subatomic particles are: (1) Electrons - negatively charged particles that orbit the nucleus; (2) Protons - positively charged…
An atom has 8 electrons and 8 protons. What is the net charge on this atom?
Answer
The net charge on the atom is zero (electrically neutral). This is because the positive charge from 8 protons (+8) exactly balances the negative charge from 8 electrons (-8). Since +8 + (-8) = 0, the …
Describe Thomson's model of the atom. What was the main idea behind it?
Answer
Thomson's model (1898) proposed that an atom is like a Christmas pudding or watermelon. The main features are: (1) The atom consists of a sphere of positive charge spread throughout; (2) Electrons are…
Why did Rutherford choose a gold foil for his alpha-particle scattering experiment instead of a thicker metal?
Answer
Rutherford chose gold foil because: (1) He wanted the thinnest possible layer of atoms to reduce interference; (2) The gold foil he used was only about 1000 atoms thick; (3) This thin layer allowed hi…
In Rutherford's alpha-particle scattering experiment, most particles passed straight through the gold foil, but some were deflected at large angles. What does this tell us about atomic structure?
Answer
This observation reveals that: (1) Most of the space inside an atom is empty (most particles pass through undeflected); (2) The positive charge of the atom occupies very little space (some particles a…
What was Rutherford's nuclear model of the atom? List its main features.
Answer
Rutherford's nuclear model proposed: (1) A positively charged nucleus exists at the center of the atom, containing most of the atom's mass; (2) Electrons revolve around the nucleus in circular paths o…
Why was Rutherford's model of the atom considered unstable? What problem did it have?
Answer
Rutherford's model had a critical flaw: According to electromagnetic theory, an electron moving in a circular orbit undergoes constant acceleration. Any charged particle undergoing acceleration should…
What is Bohr's model of the atom? What were his main postulates?
Answer
Bohr's model (1913) proposed two key postulates to solve the stability problem: (1) Only certain special orbits (called discrete orbits or energy levels) are allowed inside an atom - electrons cannot …
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