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NCERT Exemplar · Class 10 Science Periodic Classification of Elements

52 questions · 52 still being checked

Multiple Choice Questions 21–26 (part 3 of 6)

  1. Exercise 21

    Which of the following elements will form an acidic oxide?
    (a)
    An element with atomic number 7\displaystyle 7
    (b)
    An element with atomic number 3\displaystyle 3
    (c)
    An element with atomic number 12\displaystyle 12
    (d)
    An element with atomic number 19\displaystyle 19

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    NCERT’s answer
    (a)
    (a) Atomic number 7. Nitrogen is a non-metal whose oxides, \(\displaystyle \mathrm{N_2O_5}\) and \(\displaystyle \mathrm{NO_2}\), are acidic; atomic numbers $\displaystyle 3$, $\displaystyle 12$, $\displaystyle 19$ are metals (Li, Mg, K) forming basic oxides.

  2. Exercise 22

    The element with atomic number 14\displaystyle 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?
    (a)
    Metal
    (b)
    Metalloid
    (c)
    Non-metal
    (d)
    Left-hand side element

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    NCERT’s answer
    (b)
    (b) Metalloid.\[Z=14:\ 2,8,4 \Rightarrow \mathrm{Si} \]Hard like a metal, yet \(\displaystyle \mathrm{SiO_2}\) is acidic and \(\displaystyle \mathrm{SiCl_4}\) covalent, like a non-metal — traits of both, so a metalloid.

  3. Exercise 23

    Which one of the following depict the correct representation of atomic radius(r) of an atom? (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) NCERT_Question_Class10_Science_Exemplar_Ch5_Q23 NCERT_Question_Class10_Science_Exemplar_Ch5_Q23_2 NCERT_Question_Class10_Science_Exemplar_Ch5_Q23_3 NCERT_Question_Class10_Science_Exemplar_Ch5_Q23_4

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    NCERT’s answer
    (b)
    (b) (ii) and (iii).
    Radius runs from the nucleus centre to the outermost occupied shell.
    \[\text{(ii)}\ \ 1\ e^-\ \text{in K}\ \Rightarrow\ r:\ \mathrm{N}\to\mathrm{K}\ \checkmark \]
    \[\text{(iii)}\ \ 2,8,1\ \Rightarrow\ r:\ \mathrm{N}\to\mathrm{M}\ \checkmark \]
    (i)
    stays inside the nucleus; (iv) starts at shell L, not the nucleus.

  4. Exercise 24

    Which one of the following does not increase while moving down the group of the periodic table?
    (a)
    Atomic radius
    (b)
    Metallic character
    (c)
    Valence
    (d)
    Number of shells in an element

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    NCERT’s answer
    (c)
    (c) Valence.Down a group, shells and shielding grow, so atomic radius and metallic character both rise, \(\displaystyle n\uparrow \Rightarrow r\uparrow\). Valence tracks only the outermost-shell electron count, which repeats each period, so it stays fixed down a group.

  5. Exercise 25

    On moving from left to right in a period in the periodic table, the size of the atom.
    (a)
    increases
    (b)
    decreases
    (c)
    does not change appreciably
    (d)
    first decreases and then increases

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    NCERT’s answer
    (b)
    (b) Decreases.Across a period electrons keep joining the same shell while the nuclear charge grows by one proton each step; the stronger pull draws that shell inward, \(\displaystyle Z\uparrow \Rightarrow r\downarrow\).

  6. Exercise 26

    Which of the following set of elements is written in order of their increasing metallic character?
    (a)
    Be Mg Ca
    (b)
    Na Li K
    (c)
    Mg Al Si
    (d)
    C O N

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    NCERT’s answer
    (a)
    (a) Be, Mg, Ca.\[\mathrm{Be}\,(n=2) < \mathrm{Mg}\,(n=3) < \mathrm{Ca}\,(n=4) \]\[n\uparrow \Rightarrow \text{metallic character}\uparrow \]All in Group $\displaystyle 2$, listed top to bottom; the other sets are mis-ordered.