41. The atomic model proposed by J.J. Thomson is known as the:

a) Plum pudding model
b) Nuclear model
c) Planetary model
d) Quantum model
Answer: a) Plum pudding model

42. Which of the following subshells has the lowest energy in a multi-electron atom?

a) 3d
b) 4s
c) 4p
d) 3p
Answer: b) 4s

43. What is the principal quantum number of the outermost electron in a calcium atom?

a) 1
b) 2
c) 3
d) 4
Answer: d) 4

44. How many valence electrons does an oxygen atom have?

a) 4
b) 6
c) 8
d) 2
Answer: b) 6

45. Which particle contributes most to the atomic mass of an atom?

a) Proton
b) Electron
c) Neutron
d) Photon
Answer: c) Neutron

46. In the periodic table, elements are arranged according to their:

a) Atomic mass
b) Atomic number
c) Neutron number
d) Electron affinity
Answer: b) Atomic number

47. The number of orbitals in the p subshell is:

a) 1
b) 2
c) 3
d) 4
Answer: c) 3

48. Which of the following describes the uncertainty principle?

a) Exact position and momentum of a particle can be known simultaneously
b) Position and momentum of a particle cannot be precisely determined at the same time
c) Electrons are always in fixed orbits
d) Energy levels are always quantized
Answer: b) Position and momentum of a particle cannot be precisely determined at the same time

49. Which model of the atom includes electrons orbiting the nucleus in fixed paths?

a) Thomson model
b) Rutherford model
c) Bohr model
d) Quantum model
Answer: c) Bohr model

50. The maximum number of electrons that can be accommodated in the third shell is:

a) 8
b) 10
c) 18
d) 32
Answer: c) 18