07/04/2026
ATOMIC STRUCTURE — HISTORY & ATOMIC THEORIES
1. The idea that matter is made up of indivisible particles called atomos was first proposed by
A. Aristotle
B. Democritus
C. Dalton
D. Rutherford
2. The atomic theory of Democritus was rejected mainly because it
A. contradicted chemical laws
B. lacked experimental evidence
C. was mathematically incorrect
D. ignored energy changes
3. The development of atomic theory remained stagnant for many centuries because
A. experiments were forbidden
B. Aristotle opposed atomic ideas
C. metals were unknown
D. atoms were invisible
4. The first scientific atomic theory was proposed by
A. Thomson
B. Dalton
C. Bohr
D. Lavoisier
5. According to Dalton, atoms of the same element are
A. electrically charged
B. chemically unstable
C. identical in mass and properties
D. made of electrons
6. Dalton’s theory was based mainly on the
A. laws of electrolysis
B. gas laws only
C. laws of chemical combination
D. nuclear reactions
7. Which law strongly supported Dalton’s atomic theory?
A. Law of conservation of mass
B. Boyle’s law
C. Ohm’s law
D. Charles’ law
8. Dalton described atoms as
A. energy waves
B. solid indivisible spheres
C. charged clouds
D. hollow particles
9. Dalton’s theory failed to explain the existence of
A. molecules
B. compounds
C. isotopes
D. mixtures
10. Which statement contradicts Dalton’s theory?
A. Atoms combine chemically
B. Atoms are divisible
C. Compounds form in fixed ratios
D. Matter is conserved
11. The electron was discovered through the study of
A. alpha particles
B. cathode rays
C. X-rays
D. gamma rays
12. The scientist who discovered the electron was
A. Rutherford
B. Bohr
C. Thomson
D. Chadwick
13. Thomson proposed that atoms are
A. solid particles
B. positively charged spheres containing electrons
C. empty spaces
D. nuclear shells
14. Thomson’s atomic model is popularly known as the
A. Nuclear model
B. Planetary model
C. Plum pudding model
D. Quantum model
15. In Thomson’s model, electrons are
A. outside the atom
B. embedded in positive charge
C. inside the nucleus
D. stationary particles
16. Thomson concluded atoms are divisible because he discovered
A. neutrons
B. protons
C. electrons
D. nuclei
17. A major weakness of Thomson’s model was inability to explain
A. chemical bonding
B. atomic neutrality
C. alpha particle scattering
D. electron charge
18. Rutherford used which particles in his famous experiment?
A. Beta particles
B. Alpha particles
C. Electrons
D. Neutrons
19. The metal foil used in Rutherford’s experiment was
A. silver
B. copper
C. gold
D. platinum
20. Most alpha particles passed through the foil because atoms are
A. dense
B. neutral
C. mostly empty space
D. negatively charged
21. The deflection of some alpha particles indicated the presence of a
A. neutron cloud
B. dense nucleus
C. positive electron
D. hollow center
22. Rutherford concluded that atomic mass is concentrated in the
A. electron shell
B. outer orbit
C. nucleus
D. energy level
23. The Rutherford model introduced the concept of the
A. orbital
B. nucleus
C. isotope
D. quantum number
24. Rutherford’s model could not explain
A. atomic neutrality
B. electron arrangement stability
C. nuclear charge
D. scattering results
25. Bohr improved Rutherford’s model by introducing
A. electron waves
B. fixed energy levels
C. nuclear fusion
D. neutron shells
26. According to Bohr, electrons move in
A. random paths
B. elliptical clouds
C. fixed circular orbits
D. vibrating shells
27. Energy is emitted when an electron
A. moves away from nucleus
B. jumps to a higher orbit
C. falls to a lower energy level
D. stops moving
28. Bohr’s model successfully explained the spectrum of
A. helium
B. hydrogen
C. oxygen
D. neon
29. Bohr’s theory introduced the idea of energy being
A. continuous
B. conserved
C. quantized
D. destroyed
30. A limitation of Bohr’s model is that it works best for
A. heavy atoms only
B. multi-electron atoms
C. hydrogen-like atoms
D. radioactive atoms
31. The modern atomic model is based on
A. classical mechanics
B. quantum mechanics
C. thermodynamics
D. relativity only
32. The scientist associated with wave equations describing electrons is
A. Dalton
B. Schrödinger
C. Rutherford
D. Thomson
33. Heisenberg stated that it is impossible to know simultaneously the exact
A. mass and charge
B. position and momentum
C. energy and velocity
D. orbit and size
34. The modern model describes electrons as existing in
A. fixed paths
B. probability clouds
C. solid shells
D. circular tracks
35. Regions where electrons are most likely found are called
A. nuclei
B. orbitals
C. shells
D. rays
36. Wave–particle duality suggests electrons behave as
A. solids only
B. waves only
C. both particles and waves
D. charges only
37. Which model first suggested internal structure of atoms?
A. Dalton’s model
B. Thomson’s model
C. Bohr’s model
D. Quantum model
38. The discovery that atoms contain a dense center invalidated
A. Bohr’s model
B. Dalton’s model
C. Quantum theory
D. Wave theory
39. The correct chronological order is
A. Dalton → Thomson → Rutherford → Bohr
B. Thomson → Dalton → Rutherford → Bohr
C. Rutherford → Dalton → Thomson → Bohr
D. Bohr → Dalton → Thomson → Rutherford
40. Which scientist first used experimental evidence to support atomic theory?
A. Democritus
B. Dalton
C. Aristotle
D. Bohr
41. The idea of quantized energy levels originated from
A. Rutherford
B. Thomson
C. Bohr
D. Chadwick
42. Which model replaced definite orbits with probability regions?
A. Dalton model
B. Bohr model
C. Quantum mechanical model
D. Thomson model
43. The discovery of electrons proved that atoms are
A. indivisible
B. neutral particles only
C. divisible
D. unstable
44. The nuclear model of the atom was proposed in
A. 1803
B. 1897
C. 1911
D. 1926
45. The major improvement of Bohr over Rutherford was explanation of
A. nucleus formation
B. electron stability
C. proton discovery
D. neutron existence
46. Which model compared electrons to planets around the sun?
A. Thomson model
B. Rutherford model
C. Bohr model
D. Quantum model
47. The uncertainty principle applies mainly to
A. protons
B. neutrons
C. electrons
D. nuclei
48. The modern atomic theory combines concepts from
A. chemistry only
B. physics only
C. quantum physics and mathematics
D. biology and physics
49. Which discovery marked the transition from classical to modern atomic theory?
A. Dalton’s postulates
B. Electron discovery
C. Quantum mechanics development
D. Gold foil experiment
50. The present understanding of atomic structure is best described by the
A. solid sphere model
B. nuclear model
C. planetary model
D. quantum mechanical model
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