Looking for authentic SEBA Class 10 Science Chapter 5 (Periodic Classification of Elements) MCQ solutions for the 2026–27 academic year? Access complete multiple-choice questions with correct options, detailed explanations, periodic trend rules, valence electron trends, and objective notes designed to help you score top marks in your HSLC board exams.
MCQ
Q1. Who first attempted to classify elements based on similar properties?
a) Newlands
b) Mendeleev
c) Döbereiner
d) Moseley
Answer: c) Döbereiner
Q2. Döbereiner grouped elements into sets of how many?
a) 2
b) 3
c) 4
d) 5
Answer: b) 3
Q3. In Döbereiner’s Triads, the atomic mass of the middle element is:
a) The average of the other two
b) Double the first
c) Half the sum of the other two
d) Unrelated
Answer: a) The average of the other two
Q4. Which of the following is a Döbereiner’s Triad?
a) Li, Na, K
b) H, He, Li
c) B, C, N
d) Fe, Co, Ni
Answer: a) Li, Na, K
Q5. Limitation of Döbereiner’s Triads:
a) Could not arrange by mass
b) Worked only for gases
c) Only a few elements fit into triads
d) Predicted new elements
Answer: c) Only a few elements fit into triads
Q6. Who proposed the Law of Octaves?
a) Mendeleev
b) Moseley
c) Newlands
d) Döbereiner
Answer: c) Newlands
Q7. Newlands arranged elements in increasing order of:
a) Atomic number
b) Atomic mass
c) Density
d) Reactivity
Answer: b) Atomic mass
Q8. According to Newlands, every ___ element had similar properties to the first.
a) 7th
b) 8th
c) 9th
d) 10th
Answer: b) 8th
Q9. The Law of Octaves worked well only up to which element?
a) Sodium
b) Potassium
c) Calcium
d) Iron
Answer: c) Calcium
Q10. Why was Newlands’ law compared to musical notes?
a) Because it produced sound
b) Because properties repeated every eighth element, like notes repeat every eighth tone
c) Because it was related to frequencies
d) None of these
Answer: b) Because properties repeated every eighth element, like notes repeat every eighth tone
Q11. Which pair of elements was placed in the same slot by Newlands?
a) Li and Na
b) Co and Ni
c) H and He
d) C and O
Answer: b) Co and Ni
Q12. Why did Newlands’ classification fail?
a) Only 56 elements were known
b) New elements discovered didn’t fit
c) He ignored isotopes
d) Both (b) and (c)
Answer: b) New elements discovered didn’t fit
Q13. Mendeleev arranged elements in order of:
a) Atomic number
b) Atomic mass
c) Density
d) Electronegativity
Answer: b) Atomic mass
Q14. Mendeleev’s Periodic Law states:
a) Properties are periodic functions of atomic mass
b) Atomic number decides reactivity
c) Atomic mass equals atomic number
d) Isotopes behave differently
Answer: a) Properties are periodic functions of atomic mass
Q15. Mendeleev left gaps in his table for:
a) Missing compounds
b) Unknown elements
c) Noble gases
d) Isotopes
Answer: b) Unknown elements
Q16. Which element was predicted as ‘Eka-Aluminium’?
a) Scandium
b) Gallium
c) Germanium
d) Silicon
Answer: b) Gallium
Q17. Mendeleev’s predicted ‘Eka-Silicon’ turned out to be:
a) Boron
b) Germanium
c) Aluminium
d) Argon
Answer: b) Germanium
Q18. What was the main advantage of Mendeleev’s table?
a) Perfectly arranged all elements
b) Predicted new elements successfully
c) Used atomic number
d) None of these
Answer: b) Predicted new elements successfully
Q19. Hydrogen’s position was uncertain in Mendeleev’s table because:
a) It had no neutrons
b) It showed properties of both group 1 and group 17
c) It was gaseous
d) It had isotopes
Answer: b) It showed properties of both group 1 and group 17
SEBA Class 10 Science Chapter 5 MCQ Solutions
Q20. Why did isotopes cause a problem for Mendeleev’s table?
a) They had same mass
b) They had different atomic numbers
c) They had same properties but different masses
d) None of these
Answer: c) They had same properties but different masses
Q21. Who discovered that atomic number is the basis of classification?
a) Mendeleev
b) Newlands
c) Moseley
d) Bohr
Answer: c) Moseley
Q22. Modern Periodic Law states:
a) Properties are periodic functions of atomic mass
b) Properties are periodic functions of atomic number
c) Elements repeat after every 7th element
d) None of these
Answer: b) Properties are periodic functions of atomic number
Q23. The Modern Periodic Table has how many groups?
a) 7
b) 8
c) 18
d) 9
Answer: c) 18
Q24. How many periods are there in the Modern Periodic Table?
a) 6
b) 7
c) 8
d) 9
Answer: b) 7
Q25. Elements in the same group have the same:
a) Number of shells
b) Number of valence electrons
c) Atomic mass
d) Physical state
Answer: b) Number of valence electrons
Q26. Elements in the same period have the same:
a) Number of valence electrons
b) Number of shells
c) Atomic mass
d) Chemical properties
Answer: b) Number of shells
Q27. Which shell is filled in the 3rd period?
a) K
b) L
c) M
d) N
Answer: c) M
Q28. Formula to calculate maximum electrons in a shell?
a) n²
b) 2n²
c) 4n²
d) n³
Answer: b) 2n²
Q29. Atomic size across a period:
a) Increases
b) Decreases
c) Remains same
d) First increases then decreases
Answer: b) Decreases
Q30. Metallic character across a period:
a) Increases
b) Decreases
c) Remains same
d) Becomes irregular
Answer: b) Decreases
Class 10 Science Chapter 5 MCQ Question Answer SEBA 2026-27
Q31. Hydrogen resembles:
a) Alkali metals only
b) Halogens only
c) Both alkali metals and halogens
d) Noble gases
Answer: c) Both alkali metals and halogens
Q32. In Mendeleev’s Periodic Table, hydrogen could be placed in:
a) Group 1 only
b) Group 17 only
c) Both Group 1 and Group 17
d) Group 18
Answer: c) Both Group 1 and Group 17
Q33. Which property of hydrogen makes it similar to alkali metals?
a) It forms acidic oxides
b) It forms H₂ molecule
c) It forms HCl and H₂O like alkali metals
d) It has two valence electrons
Answer: c) It forms HCl and H₂O like alkali metals
Q34. Isotopes like Cl-35 and Cl-37 are placed in the same slot because they have:
a) Different atomic masses
b) Similar atomic numbers
c) Different properties
d) Same number of neutrons
Answer: b) Similar atomic numbers
Q35. How were isotopes positioned in the Modern Periodic Table?
a) In separate positions
b) In the same position
c) In the same group but different periods
d) Randomly
Answer: b) In the same position
Q36. How were cobalt and nickel’s positions resolved in the Modern Table?
a) By atomic mass
b) By arranging according to atomic number
c) By their chemical reactivity
d) By their color
Answer: b) By arranging according to atomic number
Q37. Is it possible to have an element with atomic number 1.5 between H and He?
a) Yes
b) No
c) Only if it’s an isotope
d) Only if it’s synthetic
Answer: b) No
Q38. Where is hydrogen placed in the Modern Periodic Table?
a) Group 17
b) Group 18
c) Group 1, Period 1
d) Group 2, Period 1
Answer: c) Group 1, Period 1
Q39. Which of the following elements belong to Group 1?
a) Li, Na, K
b) Be, Mg, Ca
c) C, N, O
d) F, Cl, Br
Answer: a) Li, Na, K
Q40. Electronic configuration of lithium (Li) is:
a) 2, 8, 1
b) 2, 1
c) 1, 2
d) 2, 2
Answer: b) 2, 1
Periodic Classification of Elements Class 10 SEBA MCQ Notes
Q41. What similarity is found in the electronic configurations of Li, Na, and K?
a) Same number of shells
b) Same number of valence electrons
c) Same number of protons
d) Same atomic mass
Answer: b) Same number of valence electrons
Q42. How many valence electrons are present in all Group 1 elements?
a) 2
b) 1
c) 3
d) 8
Answer: b) 1
Q43. Which elements belong to the 2nd period?
a) Li, Be, B, C, N, O, F, Ne
b) Na, Mg, Al, Si, P, S, Cl, Ar
c) H, He, Li, Be
d) K, Ca, Sc, Ti
Answer: a) Li, Be, B, C, N, O, F, Ne
Q44. Do elements in the same period have the same number of shells?
a) Yes
b) No
c) Sometimes
d) Only for metals
Answer: a) Yes
Q45. Do elements in the same period have the same valence electrons?
a) Yes
b) No
c) Depends on atomic mass
d) Depends on reactivity
Answer: b) No
Q46. How is valency determined from electronic configuration?
a) By number of shells
b) By number of valence electrons
c) By atomic mass
d) By number of isotopes
Answer: b) By number of valence electrons
Q47. Valency of magnesium (Z = 12):
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Q48. Valency of sulphur (Z = 16):
a) 2
b) 4
c) 6
d) 8
Answer: a) 2
Q49. How does valency vary across a period?
a) Remains constant
b) Increases then decreases
c) Decreases
d) Randomly changes
Answer: b) Increases then decreases
Q50. How does valency vary down a group?
a) Changes irregularly
b) Remains the same
c) Decreases
d) Doubles
Answer: b) Remains the same
SEBA Class 10 Science Chapter 5 Multiple Choice Questions
Q51. Arrange these in decreasing atomic radius: Li, Be, B, C, N, O.
a) Li > Be > B > C > N > O
b) O > N > C > B > Be > Li
c) Be > Li > B > C > N > O
d) Random order
Answer: a) Li > Be > B > C > N > O
Q52. Which element has the largest atom in Period 2?
a) O
b) N
c) Li
d) Be
Answer: c) Li
Q53. Which element has the smallest atom in Period 2?
a) F
b) O
c) C
d) N
Answer: b) O
Q54. How does atomic radius change across a period?
a) Increases
b) Decreases
c) Remains constant
d) Irregularly changes
Answer: b) Decreases
Q55. How does atomic size change down a group?
a) Increases
b) Decreases
c) Remains constant
d) First increases, then decreases
Answer: a) Increases
Q56. In Group 1, the smallest and largest atoms are:
a) Smallest – Cs, Largest – Li
b) Smallest – Li, Largest – Cs
c) Smallest – Na, Largest – K
d) Smallest – Rb, Largest – Cs
Answer: b) Smallest – Li, Largest – Cs
Q57. In the 3rd period, which elements are metals?
a) Na, Mg, Al
b) Si, P, S
c) Cl, Ar
d) B, C, N
Answer: a) Na, Mg, Al
Q58. In the 3rd period, which elements are non-metals?
a) Na, Mg
b) Si, P, S, Cl, Ar
c) Al, Si
d) Li, Be
Answer: b) Si, P, S, Cl, Ar
Q59. On which side of the Periodic Table are metals found?
a) Right
b) Left
c) Middle
d) Zig-zag line
Answer: b) Left
Q60. On which side are non-metals found?
a) Right
b) Left
c) Centre
d) Bottom
Answer: a) Right
HSLC Science Periodic Table Objective Questions
Q61. How does the tendency to lose electrons change in a group?
a) Increases down the group
b) Decreases down the group
c) Remains same
d) Varies randomly
Answer: a) Increases down the group
Q62. How does the tendency to lose electrons change across a period?
a) Increases
b) Decreases
c) Remains constant
d) Doubles
Answer: b) Decreases
Q63. How does the tendency to gain electrons change across a period?
a) Decreases
b) Increases
c) Remains constant
d) Irregularly changes
Answer: b) Increases
Q64. How does the tendency to gain electrons change down a group?
a) Increases
b) Decreases
c) Remains same
d) Doubles
Answer: b) Decreases
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