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NCERT Exemplar · Class 10 Science Periodic Classification of Elements

52 questions · 52 still being checked

Multiple Choice Questions 1–10 (part 1 of 6)

  1. Exercise 1

    Upto which element, the Law of Octaves was found to be applicable
    (a)
    Oxygen
    (b)
    Calcium
    (c)
    Cobalt
    (d)
    Potassium

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    NCERT’s answer
    (b)
    (b) CalciumNewlands' octaves matched properties only as far as calcium; beyond it, every eighth element stopped repeating the first's properties once heavier elements were added.

  2. Exercise 2

    According to Mendeléev's Periodic Law, the elements were arranged in the periodic table in the order of
    (a)
    increasing atomic number
    (b)
    decreasing atomic number
    (c)
    increasing atomic masses
    (d)
    decreasing atomic masses

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    NCERT’s answer
    (c)
    (c) increasing atomic massesMendeléev's Law states that properties recur periodically when elements are arranged by rising atomic mass, unlike the Modern Law, which uses atomic number.

  3. Exercise 3

    In Mendeléev 's Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the perioidc table later
    (a)
    Germanium
    (b)
    Chlorine
    (c)
    Oxygen
    (d)
    Silicon

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    NCERT’s answer
    (a)
    (a) GermaniumMendeléev left a gap after silicon for 'eka-silicon'; germanium, discovered in $\displaystyle 1886$, fit that gap exactly, while chlorine, oxygen and silicon were already known and placed.

  4. Exercise 4

    Which of the following statement (s) about the Modern Periodic Table are incorrect
    (i)
    The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number
    (ii)
    The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses
    (iii)
    Isotopes are placed in adjoining group (s) in the Periodic Table
    (iv)
    The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number
    (a) (i) only
    (b) (i), (ii) and (iii)
    (c) (i), (ii) and (iv)
    (d) (iv) only

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    NCERT’s answer
    (b)
    (b) (i), (ii) and (iii)The Modern Law uses increasing atomic number, not decreasing (i) or atomic mass (ii); isotopes share one atomic number, so they sit in the SAME group, not an adjoining one (iii).

  5. Exercise 5

    Which of the following statements about the Modern Periodic Table is correct:
    (a)
    It has 18\displaystyle 18 horizontal rows known as Periods
    (b)
    It has 7\displaystyle 7 vertical columns known as Periods
    (c)
    It has 18\displaystyle 18 vertical columns known as Groups
    (d)
    It has 7\displaystyle 7 horizontal rows known as Groups

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    NCERT’s answer
    (c)
    (c) It has $\displaystyle 18$ vertical columns known as GroupsThe Modern Periodic Table has $\displaystyle 18$ vertical columns (Groups) and $\displaystyle 7$ horizontal rows (Periods) -- the labelling in the other options is swapped.

  6. Exercise 6

    Which of the given elements A, B, C, D and E with atomic number 2\displaystyle 2, 3\displaystyle 3, 7\displaystyle 7, 10\displaystyle 10 and 30\displaystyle 30 respectively belong to the same period?
    (a)
    A, B, C
    (b)
    B, C, D
    (c)
    A, D, E
    (d)
    B, D, E

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    NCERT’s answer
    (b)
    (b) B, C, D\[\text{Period} = \text{number of occupied electron shells} \] \[A\ (Z{=}2):\ 2 \Rightarrow 1\ \text{shell} \Rightarrow \text{Period 1} \] \[B\ (Z{=}3):\ 2,1 \Rightarrow 2\ \text{shells} \Rightarrow \text{Period 2} \] \[C\ (Z{=}7):\ 2,5 \Rightarrow 2\ \text{shells} \Rightarrow \text{Period 2} \] \[D\ (Z{=}10):\ 2,8 \Rightarrow 2\ \text{shells} \Rightarrow \text{Period 2} \] \[E\ (Z{=}30):\ 2,8,18,2 \Rightarrow 4\ \text{shells} \Rightarrow \text{Period 4} \]

  7. Exercise 7

    The elements A, B, C, D and E have atomic number 9\displaystyle 9, 11\displaystyle 11, 17\displaystyle 17, 12\displaystyle 12 and 13\displaystyle 13 respectively. Which pair of elements belong to the same group?
    (a)
    A and B
    (b)
    B and D
    (c)
    A and C
    (d)
    D and E

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    NCERT’s answer
    (c)
    (c) A and C\[\text{Same group} \Rightarrow \text{same number of valence electrons} \] \[A\ (Z{=}9,\ \mathrm{F}):\ 2,7 \Rightarrow 7\ \text{valence } e^- \Rightarrow \text{Group 17} \] \[B\ (Z{=}11,\ \mathrm{Na}):\ 2,8,1 \Rightarrow 1\ \text{valence } e^- \Rightarrow \text{Group 1} \] \[C\ (Z{=}17,\ \mathrm{Cl}):\ 2,8,7 \Rightarrow 7\ \text{valence } e^- \Rightarrow \text{Group 17} \] \[D\ (Z{=}12,\ \mathrm{Mg}):\ 2,8,2 \Rightarrow 2\ \text{valence } e^- \Rightarrow \text{Group 2} \] \[E\ (Z{=}13,\ \mathrm{Al}):\ 2,8,3 \Rightarrow 3\ \text{valence } e^- \Rightarrow \text{Group 13} \]

  8. Exercise 8

    Where would you locate the element with electronic configuration 2,8\displaystyle 2,8 in the Modern Periodic Table?
    (a)
    Group 8\displaystyle 8
    (b)
    Group 2\displaystyle 2
    (c)
    Group 18\displaystyle 18
    (d)
    Group 10\displaystyle 10

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    NCERT’s answer
    (c)
    (c) Group $\displaystyle 18$ — \(\displaystyle 2, 8\) fills the K and L shells completely ($\displaystyle 10$ electrons), so this is neon, a noble gas with $\displaystyle 8$ valence electrons, placed in Group 18.

  9. Exercise 9

    An element which is an essential constituent of all organic compounds belongs to
    (a)
    group 1\displaystyle 1
    (b)
    group 14\displaystyle 14
    (c)
    group 15\displaystyle 15
    (d)
    group 16\displaystyle 16

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    NCERT’s answer
    (b)
    (b) group $\displaystyle 14$ — carbon, with $\displaystyle 4$ valence electrons, forms strong covalent bonds and long chains/rings, so it is the backbone atom of every organic compound.

  10. Exercise 10

    Which of the following is the outermost shell for elements of period 2\displaystyle 2?
    (a)
    K shell
    (b)
    L shell
    (c)
    M shell
    (d)
    N shell

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    NCERT’s answer
    (b)
    (b) L shell — the period number equals the number of occupied shells; period $\displaystyle 2$ elements fill the K shell, then the L shell, which is outermost.