Questions on Atomic Structure
30 Multiple-Choice Questions: Atomic Structure
1. What is the central part of an atom called?
A) Electron shell
B) Nucleus
C) Proton
D) Neutron
E) Orbital
2. Which subatomic particle has a negative charge?
A) Proton
B) Neutron
C) Electron
D) Positron
E) Nucleon
3. What is the relative charge of a proton?
A) –1
B) 0
C) +1
D) +2
E) –2
4. Where are electrons located in an atom?
A) Inside the nucleus
B) In energy levels around the nucleus
C) In protons
D) In the neutron cloud
E) In the atomic core
5. What subatomic particle has no electrical charge?
A) Proton
B) Neutron
C) Electron
D) Ion
E) Positron
6. Which particle determines the identity of an element?
A) Electron
B) Neutron
C) Proton
D) Isotope
E) Nucleus
7. What is the atomic number of an element equal to?
A) Number of electrons
B) Number of neutrons
C) Number of protons
D) Atomic mass
E) Number of orbitals
8. What is the mass number of an atom?
A) Number of protons only
B) Number of electrons only
C) Number of neutrons only
D) Sum of protons and neutrons
E) Total number of subatomic particles
9. Isotopes of an element have the same number of:
A) Neutrons
B) Protons
C) Mass numbers
D) Electrons and neutrons
E) Electrons and mass
10. Who discovered the electron?
A) Dalton
B) Rutherford
C) Bohr
D) Thomson
E) Chadwick
11. What is the charge of a neutron?
A) +1
B) –1
C) 0
D) +2
E) –2
12. What is the approximate mass of a proton?
A) 0 amu
B) 1 amu
C) 2 amu
D) 0.5 amu
E) 4 amu
13. What is the approximate mass of an electron?
A) 1 amu
B) 0.5 amu
C) 0.0005 amu
D) 0.005 amu
E) 2 amu
14. What are energy levels also called?
A) Neutron clouds
B) Proton shells
C) Electron shells
D) Atomic mass units
E) Subatomic zones
15. What particle is found in the nucleus?
A) Electron
B) Ion
C) Proton
D) Positron
E) Anion
16. Which part of the atom contains most of its mass?
A) Electron cloud
B) Shell
C) Nucleus
D) Orbital
E) Energy level
17. The number of electrons in a neutral atom equals the number of:
A) Neutrons
B) Protons
C) Isotopes
D) Nucleons
E) Valence shells
18. Which of the following is not a subatomic particle?
A) Proton
B) Electron
C) Nucleus
D) Neutron
E) All are subatomic particles
19. What is the charge of the nucleus of an atom?
A) Negative
B) Neutral
C) Positive
D) Depends on the atom
E) Zero
20. Who discovered the nucleus?
A) J.J. Thomson
B) John Dalton
C) Niels Bohr
D) Ernest Rutherford
E) James Chadwick
21. Which subatomic particles contribute to atomic mass?
A) Only protons
B) Only electrons
C) Protons and electrons
D) Protons and neutrons
E) Neutrons and electrons
22. What defines an isotope?
A) Same protons, different neutrons
B) Same neutrons, different protons
C) Same electrons, different mass
D) Same atomic number, same mass
E) Different elements entirely
23. Which term describes atoms with different numbers of electrons?
A) Neutrons
B) Ions
C) Isotopes
D) Compounds
E) Nucleons
24. What is the charge of a neutral atom?
A) +1
B) –1
C) 0
D) +2
E) Variable
25. What unit is used to express atomic mass?
A) Gram
B) Kilogram
C) Newton
D) Dalton or amu
E) Mole
26. Which model of the atom introduced energy levels?
A) Dalton model
B) Rutherford model
C) Bohr model
D) Plum pudding model
E) Quantum mechanical model
27. What happens to electrons in an ion with a negative charge?
A) Electrons are lost
B) Neutrons are gained
C) Electrons are gained
D) Protons are lost
E) Mass increases
28. What is an ion with more protons than electrons called?
A) Anion
B) Cation
C) Neutral atom
D) Neutron
E) Molecule
29. What is the electron cloud?
A) The region where electrons are likely to be found
B) A group of neutrons
C) The charged part of the nucleus
D) The orbit of protons
E) A radioactive field
30. How are electrons arranged in atoms?
A) Randomly in space
B) In pairs in the nucleus
C) In fixed orbits called shells or energy levels
D) In the neutron core
E) In liquid layers
Answer Key with Explanations
1. B – The nucleus is the atom’s central core.
2. C – Electrons have a negative charge.
3. C – Protons are positively charged (+1).
4. B – Electrons are found in energy levels/orbitals around the nucleus.
5. B – Neutrons are neutral particles.
6. C – The number of protons determines the element.
7. C – Atomic number = number of protons.
8. D – Mass number = protons + neutrons.
9. B – Isotopes have the same protons but different neutrons.
10. D – J.J. Thomson discovered the electron.
11. C – Neutrons have no charge.
12. B – A proton has about 1 atomic mass unit.
13. C – Electron mass is about 0.0005 amu.
14. C – Energy levels = electron shells.
15. C – Protons are in the nucleus.
16. C – The nucleus holds most of the atom’s mass.
17. B – In a neutral atom, electrons = protons.
18. C – The nucleus is a structure, not a particle.
19. C – Nucleus is positively charged (due to protons).
20. D – Rutherford discovered the nucleus with his gold foil experiment.
21. D – Mass = protons + neutrons.
22. A – Isotopes have same protons, different neutrons.
23. B – Atoms with different electrons are ions.
24. C – Neutral atoms have no charge.
25. D – Atomic mass is expressed in amu (Dalton).
26. C – Bohr model introduced energy levels.
27. C – Gaining electrons creates negative ions.
28. B – Cations have more protons than electrons.
29. A – Electron cloud is the area where electrons are likely found.
30. C – Electrons are arranged in energy levels.
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