Short QAs
1. What is atomic number?
2. What does the atomic number of an element represent?
3. What is the atomic number of hydrogen?
4. What is the atomic number of sodium?
5. In a neutral atom, what is the relationship between protons and electrons?
6. What is mass number?
7. What are nucleons?
8. Write the formula for mass number.
9. How can the number of neutrons be calculated?
10. What is the mass number of an atom having 11 protons and 12 neutrons?
11. How is an atom represented symbolically?
12. What does A represent in atomic notation?
13. What does Z represent in atomic notation?
14. Define isobars.
15. Give one example of isobars.
16. What is common in isobars?
17. Why do isobars have different chemical properties?
18. Define isotopes.
19. Give one example of isotopes.
20. What is common in isotopes?
21. Why do isotopes have similar chemical properties?
22. How many isotopes does hydrogen have?
23. Name the three isotopes of hydrogen.
24. How many neutrons are present in protium?
25. How many neutrons are present in deuterium?
26. How many neutrons are present in tritium?
27. Which isotope of hydrogen is most abundant?
28. What is the atomic number of all hydrogen isotopes?
29. Which carbon isotope is radioactive?
30. Name the isotopes of carbon.
31. Name the isotopes of chlorine.
32. What is the atomic number of bromine?
33. How many neutrons are present in bromine-80?
34. What is the atomic number of sulphur?
35. State one difference between isotopes and isobars.
36. What is the charge on the sulphide ion (S2- )?
37. Which particles determine the chemical properties of an element?
38. Which particles contribute mainly to the mass of an atom?
39. Do isotopes have the same physical properties?
40. Why is atomic number important?
41. What is the number of protons in a neutral sodium atom?
42. What is the number of electrons in a neutral bromine atom?
43. Which particles are present in the nucleus of an atom?
44. What is the formula for calculating neutrons from mass number and atomic number?
45. Why are protons called positively charged particles?
46. What is the mass number of carbon-14?
47. What is the atomic number of carbon?
48. How many neutrons are present in carbon-14?
49. How many neutrons are present in chlorine-35?
50. How many neutrons are present in chlorine-37?
MCQs
1. The atomic number of an element is equal to the number of:
A) Neutrons
B) Protons
C) Nucleons
D) Isotopes
2. In a neutral atom, the number of electrons is equal to the number of:
A) Neutrons
B) Nucleons
C) Protons
D) Isotopes
3. The mass number of an atom is the sum of:
A) Protons and electrons
B) Electrons and neutrons
C) Protons and neutrons
D) Only neutrons
4. Which particles are collectively called nucleons?
A) Electrons and protons
B) Protons and neutrons
C) Electrons and neutrons
D) Electrons only
5. The number of neutrons in an atom is given by:
A) Z + A
B) A × Z
C) A − Z
D) Z − A
6. The atomic number of hydrogen is:
A) 0
B) 1
C) 2
D) 3
7. The atomic number of sodium is:
A) 10
B) 11
C) 12
D) 23
8. Which notation correctly represents an atom?
A) XZA
B) ZXA
C) ᴬZX
D) AXZ
9. In atomic notation, A represents:
A) Atomic number
B) Number of electrons
C) Number of neutrons
D) Mass number
10. In atomic notation, Z represents:
A) Atomic number
B) Mass number
C) Number of neutrons
D) Valency
11. Atoms having the same mass number but different atomic numbers are called:
A) Isotopes
B) Isobars
C) Isotones
D) Ions
12. Atoms having the same atomic number but different mass numbers are called:
A) Isobars
B) Molecules
C) Isotopes
D) Radicals
13. Isobars have:
A) Same atomic number
B) Same mass number
C) Same number of neutrons
D) Same electrons
14. Isotopes have:
A) Same mass number
B) Different atomic numbers
C) Same atomic number
D) Different elements
15. Chemical properties of isotopes are:
A) Completely different
B) Similar
C) Opposite
D) Unrelated
16. The isotope of hydrogen with no neutron is:
A) Tritium
B) Deuterium
C) Protium
D) Hydrogen-4
17. The isotope of hydrogen containing one neutron is:
A) Protium
B) Deuterium
C) Tritium
D) Helium
18. The isotope of hydrogen containing two neutrons is:
A) Protium
B) Deuterium
C) Tritium
D) Carbon-14
19. The most abundant isotope of hydrogen is:
A) Tritium
B) Deuterium
C) Protium
D) Hydrogen-2
20. Carbon-12, Carbon-13 and Carbon-14 are:
A) Isobars
B) Isotopes
C) Isotones
D) Ions
21. Chlorine-35 and Chlorine-37 are:
A) Isobars
B) Isotopes
C) Isotones
D) Molecules
22. Which carbon isotope is radioactive?
A) Carbon-12
B) Carbon-13
C) Carbon-14
D) Carbon-15
23. Bromine-80 has atomic number 35. Its number of neutrons is:
A) 35
B) 45
C) 80
D) 115
24. The atomic number of sulphur is:
A) 14
B) 15
C) 16
D) 17
25. Which particle determines the chemical properties of an element?
A) Proton
B) Neutron
C) Electron
D) Nucleus
26. The mass of an atom is mainly concentrated in the:
A) Electron cloud
B) Orbit
C) Nucleus
D) Shell
27. The atomic number of carbon is:
A) 4
B) 5
C) 6
D) 12
28. The number of neutrons in Carbon-14 is:
A) 6
B) 7
C) 8
D) 14
29. The number of neutrons in Chlorine-35 is:
A) 17
B) 18
C) 19
D) 20
30. The number of neutrons in Chlorine-37 is:
A) 18
B) 19
C) 20
D) 21
31. Which pair represents isobars?
A) ¹²C and ¹⁴C
B) ³⁵Cl and ³⁷Cl
C) ¹⁴C and ¹⁴N
D) ¹H and ²H
32. Which pair represents isotopes?
A) ¹⁴C and ¹⁴N
B) ⁴⁰Ar and ⁴⁰Ca
C) ³⁵Cl and ³⁷Cl
D) ⁵⁸Fe and ⁵⁸Ni
33. The positive charge of the nucleus is due to:
A) Neutrons
B) Electrons
C) Protons
D) Photons
34. An atom with atomic number 11 contains:
A) 11 neutrons
B) 11 protons
C) 22 protons
D) 23 protons
35. The charge on S²⁻ ion is:
A) +2
B) +1
C) −1
D) −2
36. Which of the following is an isotope of hydrogen?
A) Deuterium
B) Nitrogen
C) Helium
D) Oxygen
37. Isobars belong to:
A) Same element
B) Different elements
C) Same compound
D) Same molecule
38. Isotopes differ in the number of:
A) Protons
B) Electrons
C) Neutrons
D) Protons and electrons
39. The number of protons in Carbon-14 is:
A) 6
B) 8
C) 12
D) 14
40. The atomic number uniquely identifies:
A) A molecule
B) An isotope
C) An element
D) A compound