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NCERT Exemplar · Class 10 Science Periodic Classification of Elements

52 questions · 52 still being checked

Multiple Choice Questions 11–20 (part 2 of 6)

  1. Exercise 11

    Which one of the following elements exhibit maximum number of valence electrons?
    (a)
    Na
    (b)
    Al
    (c)
    Si

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    NCERT’s answer
    (d)
    (d) P — valence electrons rise across period $\displaystyle 3$: Na \(\displaystyle 1\), Al \(\displaystyle 3\), Si \(\displaystyle 4\), P \(\displaystyle 5\); phosphorus has the most among these four.

  2. Exercise 12

    Which of the following gives the correct increasing order of the atomic radii of O, F and N ?
    (a)
    O, F, N
    (b)
    N, F, O
    (c)
    O, N, F
    (d)
    F, O, N

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    NCERT’s answer
    (d)
    (d) F, O, N — across period $\displaystyle 2$, \(\displaystyle Z_{eff}\uparrow \Rightarrow r\downarrow\), so radius falls N > O > F; listed smallest to largest that is F, O, N.

  3. Exercise 13

    Which among the following elements has the largest atomic radii?
    (a)
    Na
    (b)
    Mg
    (c)
    K (d) Ca

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    NCERT’s answer
    (c)
    (c) K — radius grows down a group (\(\displaystyle n\uparrow \Rightarrow r\uparrow\)) and shrinks across a period; K, the group $\displaystyle 1$ element in period $\displaystyle 4$, is largest among Na, Mg, K, Ca.

  4. Exercise 14

    Which of the following elements would lose an electron easily?
    (a)
    Mg
    (b)
    Na
    (c)
    K (d) Ca

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    NCERT’s answer
    (c)
    (c) K — losing an electron needs low ionisation energy, which falls down a group; K's valence electron sits farthest from the nucleus among Mg, Na, K, Ca, so it is removed most easily.

  5. Exercise 15

    Which of the following elements does not lose an electron easily?
    (a)
    Na
    (b)
    F (c) Mg
    (d)
    Al

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    NCERT’s answer
    (b)
    (b) F. Fluorine has $\displaystyle 7$ valence electrons and strong electronegativity, so it gains an electron to complete its octet instead of losing one; Na, Mg, Al are metals that lose electrons readily.

  6. Exercise 16

    Which of the following are the characteristics of isotopes of an element?
    (i)
    Isotopes of an element have same atomic masses
    (ii)
    Isotopes of an element have same atomic number
    (iii)
    Isotopes of an element show same physical properties
    (iv)
    Isotopes of an element show same chemical properties
    (a) (i), (iii) and (iv)
    (b) (ii), (iii) and (iv)
    (c) (ii) and (iii)
    (d) (ii) and (iv)

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    NCERT’s answer
    (d)
    (d) (ii) and (iv). Isotopes share the same atomic number (proton count) and hence identical chemical properties, but differing neutron number gives different atomic masses and mass-dependent physical properties.

  7. Exercise 17

    Arrange the following elements in the order of their decreasing metallic character
    Na, Si, Cl, Mg, Al
    (a)
    Cl>Si>Al>Mg>Na\displaystyle \mathrm{Cl}>\mathrm{Si}>\mathrm{Al}>\mathrm{Mg}>\mathrm{Na}
    (b)
    Na>Mg>Al>Si>Cl\displaystyle \mathrm{Na}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Si}>\mathrm{Cl}
    (c)
    Na>Al>Mg>Cl>Si\displaystyle \mathrm{Na}>\mathrm{Al}>\mathrm{Mg}>\mathrm{Cl}>\mathrm{Si}
    (d)
    Al>Na>Si>Ca>Mg\displaystyle \mathrm{Al}>\mathrm{Na}>\mathrm{Si}>\mathrm{Ca}>\mathrm{Mg}

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    NCERT’s answer
    (b)
    (b) \(\displaystyle \mathrm{Na} > \mathrm{Mg} > \mathrm{Al} > \mathrm{Si} > \mathrm{Cl}\). Metallic character falls left to right across Period $\displaystyle 3$ as nuclear charge rises and atomic radius shrinks.

  8. Exercise 18

    Arrange the following elements in the order of their increasing non-metallic character
    Li, O, C, Be, F
    (a)
    F<O<C<Be<Li\displaystyle \mathrm{F}<\mathrm{O}<\mathrm{C}<\mathrm{Be}<\mathrm{Li}
    (b)
    Li<Be<C<O<F\displaystyle \mathrm{Li}<\mathrm{Be}<\mathrm{C}<\mathrm{O}<\mathrm{F}
    (c)
    F<O<C<Be<Li\displaystyle \mathrm{F}<\mathrm{O}<\mathrm{C}<\mathrm{Be}<\mathrm{Li}
    (d)
    F<O<Be<C<Li\displaystyle \mathrm{F}<\mathrm{O}<\mathrm{Be}<\mathrm{C}<\mathrm{Li}

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    NCERT’s answer
    (b)
    (b) \(\displaystyle \mathrm{Li} < \mathrm{Be} < \mathrm{C} < \mathrm{O} < \mathrm{F}\). Non-metallic character rises left to right across Period $\displaystyle 2$ as atoms hold electrons more tightly.

  9. Exercise 19

    What type of oxide would Eka– aluminium form?
    (a)
    EO3\displaystyle \mathrm{EO}_3
    (b)
    E3O2\displaystyle \mathrm{E}_3 \mathrm{O}_2
    (c)
    E2O3\displaystyle \mathrm{E}_2 \mathrm{O}_3
    (d)
    EO\displaystyle \mathrm{EO}

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    NCERT’s answer
    (c)
    (c) \(\displaystyle \mathrm{E_2O_3}\). Eka-aluminium (gallium) sits below aluminium in the same group, so it forms the same oxide type as \(\displaystyle \mathrm{Al_2O_3}\), with the element in the +$\displaystyle 3$ state.

  10. Exercise 20

    Three elements B, Si and Ge are
    (a)
    metals
    (b)
    non-metals
    (c)
    metalloids
    (d)
    metal, non-metal and metalloid respectively

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    (c)
    (c) Metalloids. B, Si and Ge lie along the periodic table's diagonal staircase, sharing properties between metals and non-metals rather than being purely one or the other.