11. The smallest particle of an element that retains the properties of the element is:

a) Molecule
b) Atom
c) Electron
d) Neutron
Answer: b) Atom

12. Which subatomic particle has a positive charge?

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

13. Who proposed the nuclear model of the atom?

a) Niels Bohr
b) J.J. Thomson
c) Ernest Rutherford
d) John Dalton
Answer: c) Ernest Rutherford

14. The discovery of the electron is attributed to:

a) Niels Bohr
b) J.J. Thomson
c) Ernest Rutherford
d) James Chadwick
Answer: b) J.J. Thomson

15. In which part of the atom is the nucleus located?

a) Outer shell
b) Electron cloud
c) Center
d) Orbitals
Answer: c) Center

16. What is the charge of a neutron?

a) Positive
b) Negative
c) Neutral
d) Variable
Answer: c) Neutral

17. The mass number of an atom is the sum of:

a) Protons and neutrons
b) Electrons and protons
c) Neutrons only
d) Electrons only
Answer: a) Protons and neutrons

18. Isotopes of an element differ in their number of:

a) Protons
b) Electrons
c) Neutrons
d) Photons
Answer: c) Neutrons

19. The electron configuration of an atom describes:

a) The number of protons
b) The arrangement of electrons
c) The number of neutrons
d) The atomic mass
Answer: b) The arrangement of electrons

20. Which principle states that no two electrons in the same atom can have identical quantum numbers?

a) Hund’s Rule
b) Aufbau Principle
c) Pauli Exclusion Principle
d) Bohr’s Model
Answer: c) Pauli Exclusion Principle