Structure of the Atom
Gujarat Board · Class 9 · Science
Flashcards for Structure of the Atom — Gujarat Board Class 9 Science. Quick Q&A cards covering key concepts, definitions, and formulas.
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What are the three fundamental subatomic particles found in an atom?
Answer
The three fundamental subatomic particles are: 1. Electrons (e⁻) - negatively charged, negligible mass 2. Protons (p⁺) - positively charged, mass = 1 unit 3. Neutrons (n) - no charge, mass = 1 unit…
Describe Thomson's 'plum pudding' model of the atom.
Answer
Thomson's model proposed that: • An atom consists of a positively charged sphere • Electrons are embedded in this positive sphere like currants in a Christmas pudding • The positive and negative charg…
What were the key observations in Rutherford's alpha-particle scattering experiment?
Answer
Key observations: 1. Most α-particles passed straight through the gold foil 2. Some α-particles were deflected by small angles 3. Very few (1 in 12,000) α-particles bounced back at 180° This led to th…
State the main features of Rutherford's nuclear model of the atom.
Answer
Rutherford's nuclear model features: 1. There is a positively charged center called the nucleus 2. Nearly all the mass of the atom is in the nucleus 3. Electrons revolve around the nucleus in circular…
What was the main drawback of Rutherford's atomic model?
Answer
The main drawback was that it could not explain the stability of atoms. According to classical physics, revolving electrons should continuously lose energy and spiral into the nucleus, making atoms un…
State Bohr's postulates about the atomic model.
Answer
Bohr's postulates: 1. Only certain special orbits (discrete orbits) are allowed for electrons inside the atom 2. While revolving in these discrete orbits, electrons do not radiate energy 3. These orbi…
What is the maximum number of electrons that can be accommodated in any shell? Give the formula.
Answer
The maximum number of electrons in any shell is given by the formula 2n², where n is the shell number. Examples: • K shell (n=1): 2×1² = 2 electrons • L shell (n=2): 2×2² = 8 electrons • M shell (n=3)…
What are the rules for electron distribution in different shells (Bohr-Bury scheme)?
Answer
Rules for electron distribution: 1. Maximum electrons in a shell = 2n² 2. Maximum electrons in outermost shell = 8 3. Electrons fill inner shells first (step-wise filling) 4. Shells are filled in orde…
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