Q.1 Who proposed the planetary model of the atom?
J.J. Thomson
Ernest Rutherford
Niels Bohr
James Chadwick
Explanation - Niels Bohr proposed the planetary model of the atom in 1913, where electrons revolve around the nucleus in fixed energy levels.
Correct answer is: Niels Bohr
Q.2 Which particle has a negative charge?
Proton
Neutron
Electron
Photon
Explanation - Electrons are negatively charged subatomic particles found outside the nucleus of an atom.
Correct answer is: Electron
Q.3 Which experiment led to the discovery of the atomic nucleus?
Photoelectric effect
Rutherford gold foil experiment
Millikan oil drop experiment
Thomson's cathode ray experiment
Explanation - Rutherford's gold foil experiment in 1911 showed that atoms have a dense positively charged nucleus.
Correct answer is: Rutherford gold foil experiment
Q.4 The mass number of an atom is the sum of:
Protons and electrons
Protons and neutrons
Neutrons and electrons
Electrons only
Explanation - Mass number is the total number of protons and neutrons in an atom's nucleus.
Correct answer is: Protons and neutrons
Q.5 Which of the following has no electric charge?
Proton
Neutron
Electron
Positron
Explanation - Neutrons are neutral particles found in the nucleus of an atom with no electric charge.
Correct answer is: Neutron
Q.6 Who discovered the electron?
Ernest Rutherford
J.J. Thomson
Niels Bohr
Marie Curie
Explanation - J.J. Thomson discovered the electron in 1897 through his cathode ray experiment.
Correct answer is: J.J. Thomson
Q.7 The atomic number of an element represents:
Number of neutrons
Number of protons
Number of electrons
Sum of protons and neutrons
Explanation - The atomic number is equal to the number of protons in the nucleus of an atom and determines the element's identity.
Correct answer is: Number of protons
Q.8 Isotopes of an element differ in:
Number of protons
Number of neutrons
Number of electrons
Chemical properties
Explanation - Isotopes have the same number of protons but different numbers of neutrons, leading to different mass numbers.
Correct answer is: Number of neutrons
Q.9 The quantum number that indicates the shape of an orbital is:
Principal quantum number (n)
Azimuthal quantum number (l)
Magnetic quantum number (m)
Spin quantum number (s)
Explanation - The azimuthal (angular momentum) quantum number 'l' determines the shape of an orbital (s, p, d, f).
Correct answer is: Azimuthal quantum number (l)
Q.10 Which quantum number describes the orientation of an orbital?
Principal quantum number (n)
Azimuthal quantum number (l)
Magnetic quantum number (m)
Spin quantum number (s)
Explanation - The magnetic quantum number 'm' specifies the orientation of the orbital in space relative to other orbitals.
Correct answer is: Magnetic quantum number (m)
Q.11 Which subatomic particle determines the chemical behavior of an atom?
Proton
Neutron
Electron
Photon
Explanation - Electrons, especially the valence electrons, determine the chemical reactivity and bonding of an atom.
Correct answer is: Electron
Q.12 In Bohr’s model, electrons revolve around the nucleus in:
Random paths
Fixed energy levels
Circular orbits with varying energy
Spiral paths
Explanation - Bohr proposed that electrons move in fixed orbits or shells with quantized energy without radiating energy.
Correct answer is: Fixed energy levels
Q.13 Which is the heaviest subatomic particle?
Electron
Proton
Neutron
Alpha particle
Explanation - The neutron is slightly heavier than the proton and much heavier than the electron.
Correct answer is: Neutron
Q.14 The spin quantum number can have values of:
0, 1
+1/2, -1/2
1, 2, 3
Any integer
Explanation - Spin quantum number 's' describes the intrinsic spin of an electron and can only be +1/2 or -1/2.
Correct answer is: +1/2, -1/2
Q.15 Which scientist suggested that atoms are indivisible?
Democritus
John Dalton
J.J. Thomson
Ernest Rutherford
Explanation - John Dalton proposed that atoms are indivisible, solid spheres in his atomic theory (1803).
Correct answer is: John Dalton
Q.16 The dual nature of electrons (particle and wave) was proposed by:
Einstein
de Broglie
Bohr
Rutherford
Explanation - Louis de Broglie proposed that electrons exhibit both particle and wave properties, leading to the concept of matter waves.
Correct answer is: de Broglie
Q.17 Which shell can hold a maximum of 18 electrons?
K-shell
L-shell
M-shell
N-shell
Explanation - The M-shell (n=3) can hold up to 2n² = 2×3² = 18 electrons.
Correct answer is: M-shell
Q.18 Which element has 6 protons in its nucleus?
Oxygen
Carbon
Nitrogen
Helium
Explanation - Carbon has atomic number 6, which means it has 6 protons in its nucleus.
Correct answer is: Carbon
Q.19 The uncertainty principle is associated with:
Heisenberg
Bohr
Rutherford
Planck
Explanation - Heisenberg's uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a particle.
Correct answer is: Heisenberg
Q.20 Which orbital can hold a maximum of 10 electrons?
s-orbital
p-orbital
d-orbital
f-orbital
Explanation - A d-subshell has 5 orbitals, each of which can hold 2 electrons, totaling 10 electrons.
Correct answer is: d-orbital
Q.21 Which of the following is an alpha particle?
Electron
Proton
Helium nucleus
Neutron
Explanation - An alpha particle consists of 2 protons and 2 neutrons, identical to a helium nucleus.
Correct answer is: Helium nucleus
Q.22 The Rutherford model failed to explain:
Atomic mass
Electron stability
Number of protons
Neutron existence
Explanation - According to classical physics, orbiting electrons should radiate energy and spiral into the nucleus, which Rutherford's model could not explain.
Correct answer is: Electron stability
Q.23 Which of the following represents the principal quantum number?
n
l
m
s
Explanation - The principal quantum number 'n' indicates the main energy level or shell of an electron.
Correct answer is: n
Q.24 Which subatomic particle was discovered by Chadwick in 1932?
Proton
Electron
Neutron
Positron
Explanation - James Chadwick discovered the neutron in 1932, completing the basic structure of the atom.
Correct answer is: Neutron
Q.25 Which of the following is NOT part of Dalton's atomic theory?
Atoms are indivisible
All atoms of an element are identical
Atoms combine in simple ratios
Atoms have subatomic particles
Explanation - Dalton's theory did not include subatomic particles; this was discovered later.
Correct answer is: Atoms have subatomic particles