Questions on Atomic Number
20 Multiple-Choice Questions on Atomic Number
1. What does the atomic number of an element represent?
A) The number of electrons in a neutral atom
B) The number of neutrons
C) The atomic mass
D) The number of valence electrons
E) The number of energy levels
2. The atomic number of carbon is 6. How many protons does it have?
A) 3
B) 6
C) 8
D) 12
E) 14
3. Which subatomic particle determines the atomic number?
A) Electron
B) Neutron
C) Proton
D) Nucleus
E) Quark
4. Which of the following elements has an atomic number of 1?
A) Helium
B) Hydrogen
C) Oxygen
D) Nitrogen
E) Lithium
5. If an atom has 11 protons, what is its atomic number?
A) 22
B) 1
C) 11
D) 5
E) 6
6. How does the atomic number change across a period on the periodic table?
A) Decreases
B) Stays the same
C) Increases
D) Doubles
E) Becomes zero
7. In a neutral atom, the atomic number also indicates:
A) The number of isotopes
B) The mass number
C) The number of electrons
D) The number of neutrons
E) The atomic radius
8. What is the atomic number of oxygen?
A) 6
B) 8
C) 10
D) 12
E) 14
9. Which element has atomic number 26?
A) Copper
B) Iron
C) Zinc
D) Silver
E) Chromium
10. The atomic number is written in which position in a nuclear symbol (e.g., ⁶₃Li)?
A) Superscript
B) Subscript
C) Next to the element symbol
D) In brackets
E) Not written at all
11. The periodic table is arranged in order of:
A) Atomic mass
B) Number of neutrons
C) Atomic radius
D) Atomic number
E) Energy levels
12. How is the atomic number useful in identifying an element?
A) It tells the color of the element
B) It is unique to each element
C) It varies in isotopes
D) It shows the element’s mass
E) It describes chemical bonds
13. The atomic number of an element is always:
A) A whole number
B) A decimal
C) Larger than its mass number
D) Equal to its neutron number
E) Zero for noble gases
14. What would be the atomic number of an atom with 15 electrons?
A) 10
B) 5
C) 15
D) 20
E) 25
15. Which of the following has an atomic number of 10?
A) Neon
B) Nitrogen
C) Sodium
D) Fluorine
E) Magnesium
16. Which particle number can change in isotopes without affecting atomic number?
A) Protons
B) Electrons
C) Neutrons
D) Quarks
E) Valence electrons
17. What happens to the atomic number when a neutral atom becomes a positive ion?
A) It increases
B) It decreases
C) It stays the same
D) It becomes zero
E) It doubles
18. Which statement is true about atomic number and periodic position?
A) Atomic number decreases down a group
B) Elements in the same group have the same atomic number
C) Each element has a unique atomic number
D) Atomic number equals atomic mass
E) Atomic number varies with temperature
19. The atomic number of an element determines its:
A) Isotopic identity
B) Physical state
C) Position in the periodic table
D) Atomic mass
E) Melting point
20. Which of these pairs are correctly matched?
A) Sodium – Atomic number 12
B) Carbon – Atomic number 8
C) Oxygen – Atomic number 6
D) Nitrogen – Atomic number 7
E) Neon – Atomic number 9
- Questions on Dalton’s Atomic Theory
- Questions on Atomic Structure
- Questions on Protons, Electrons, and Neutrons
Answer Key with Explanations
1. A – The atomic number equals the number of protons, which equals the number of electrons in a neutral atom.
2. B – Carbon has 6 protons, so atomic number = 6.
3. C – The proton count defines the atomic number.
4. B – Hydrogen has atomic number 1.
5. C – An atom with 11 protons has atomic number 11.
6. C – Atomic number increases from left to right in a period.
7. C – In neutral atoms, electrons = protons = atomic number.
8. B – Oxygen has atomic number 8.
9. B – Iron (Fe) has atomic number 26.
10. B – Atomic number is written as a subscript (₈O).
11. D – The periodic table is arranged by atomic number.
12. B – Atomic number is unique to each element.
13. A – Atomic number is always a whole number.
14. C – 15 electrons → atomic number 15 (Phosphorus).
15. A – Neon has atomic number 10.
16. C – Neutrons can change in isotopes; protons (atomic number) remain constant.
17. C – Ionization does not change atomic number.
18. C – Each element has a unique atomic number.
19. C – The periodic position depends on the atomic number.
20. D – Nitrogen has atomic number 7.
Share Online!
