Atomic Structure MCQs
1. What is the central part of an atom called?
a) Electron
b) Proton
c) Neutron
d) Nucleus
Answer: d) Nucleus
2. What particles are found in the nucleus of an atom?
a) Electrons and protons
b) Protons and neutrons
c) Neutrons and electrons
d) Protons only
Answer: b) Protons and neutrons
3. Which particle in the atom has a negative charge?
a) Proton
b) Neutron
c) Electron
d) Positron
Answer: c) Electron
4. The number of protons in the nucleus of an atom is known as:
a) Atomic mass
b) Atomic number
c) Neutron number
d) Isotope number
Answer: b) Atomic number
5. Isotopes of an element have the same number of:
a) Neutrons
b) Electrons
c) Protons
d) Neutrons and protons
Answer: c) Protons
6. What determines the chemical properties of an element?
a) Number of neutrons
b) Number of protons
c) Number of electrons
d) Number of nuclei
Answer: c) Number of electrons
7. What is the maximum number of electrons that can occupy the second shell of an atom?
a) 2
b) 8
c) 18
d) 32
Answer: b) 8
8. Which principle states that electrons fill orbitals starting from the lowest energy level?
a) Pauli Exclusion Principle
b) Aufbau Principle
c) Hund’s Rule
d) Heisenberg Uncertainty Principle
Answer: b) Aufbau Principle
9. In which part of the atom do you find neutrons?
a) Orbitals
b) Nucleus
c) Electron cloud
d) Proton shell
Answer: b) Nucleus
10. Which quantum number represents the shape of an atomic orbital?
a) Principal quantum number
b) Angular momentum quantum number
c) Magnetic quantum number
d) Spin quantum number
Answer: b) Angular momentum quantum number
11. What is the region around the nucleus where electrons are most likely to be found called?
a) Shell
b) Orbital
c) Cloud
d) Subshell
Answer: b) Orbital
12. Which subatomic particle has no charge?
a) Proton
b) Electron
c) Neutron
d) Positron
Answer: c) Neutron
13. How many electrons can the third shell of an atom hold?
a) 8
b) 18
c) 32
d) 2
Answer: b) 18
14. What term describes the electrons in the outermost shell of an atom?
a) Valence electrons
b) Core electrons
c) Inner electrons
d) Subshell electrons
Answer: a) Valence electrons
15. What is the smallest unit of an element that retains its chemical properties?
a) Molecule
b) Atom
c) Compound
d) Ion
Answer: b) Atom
16. The concept that electrons occupy the lowest available energy levels first is known as:
a) Hund’s Rule
b) Pauli Exclusion Principle
c) Aufbau Principle
d) Heisenberg Principle
Answer: c) Aufbau Principle
17. What is the charge of a proton?
a) Neutral
b) Positive
c) Negative
d) Variable
Answer: b) Positive
18. Which particle determines the identity of an element?
a) Neutron
b) Electron
c) Proton
d) Positron
Answer: c) Proton
19. Which of the following describes an atom with a different number of neutrons but the same number of protons?
a) Ion
b) Isotope
c) Molecule
d) Isomer
Answer: b) Isotope
20. What term describes the weighted average mass of all naturally occurring isotopes of an element?
a) Atomic number
b) Atomic mass
c) Mass number
d) Isotopic mass
Answer: b) Atomic mass
21. Which type of orbital has a dumbbell shape?
a) s orbital
b) p orbital
c) d orbital
d) f orbital
Answer: b) p orbital
22. How are electrons arranged in an atom according to the quantum mechanical model?
a) In fixed orbits
b) Randomly
c) In regions of probability called orbitals
d) In concentric circles
Answer: c) In regions of probability called orbitals
23. The number of protons plus the number of neutrons in the nucleus is known as:
a) Atomic number
b) Mass number
c) Atomic mass
d) Neutron number
Answer: b) Mass number
24. The concept that no two electrons in an atom can have the same set of quantum numbers is known as:
a) Aufbau Principle
b) Hund’s Rule
c) Pauli Exclusion Principle
d) Heisenberg Uncertainty Principle
Answer: c) Pauli Exclusion Principle
25. Which subatomic particle is responsible for the chemical behavior of an atom?
a) Neutron
b) Proton
c) Electron
d) Photon
Answer: c) Electron
26. In the Bohr model of the atom, how are electrons arranged?
a) In elliptical orbits
b) In circular orbits around the nucleus
c) Randomly within a cloud
d) In fixed planes
Answer: b) In circular orbits around the nucleus
27. Which of the following best describes the electron cloud model?
a) Electrons are in fixed orbits
b) Electrons are in fixed shells
c) Electrons are found in probabilistic regions around the nucleus
d) Electrons move in a straight line
Answer: c) Electrons are found in probabilistic regions around the nucleus
28. How many orbitals are in the d subshell?
a) 1
b) 3
c) 5
d) 7
Answer: c) 5
29. What determines the number of electrons an atom can have in its outermost shell?
a) Atomic number
b) Number of protons
c) Number of neutrons
d) Number of shells
Answer: d) Number of shells
30. Which quantum number describes the orientation of an orbital in space?
a) Principal quantum number
b) Angular momentum quantum number
c) Magnetic quantum number
d) Spin quantum number
Answer: c) Magnetic quantum number