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3. Classification of elements and periodicity in properties — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry3. Classification of elements and periodicity in properties1 Mark
MCQ
Following statements regarding the periodic trends of chemical reactivity of the alkali metals and the halogens are given. Which of these statements gives the correct picture?
  • ✓
    Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens
  • B
    In alkali metals the reactivity increases but in the halogens it decreases with increase in atomic number down the group
  • C
    The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number down the group
  • D
    In both the alkali metals and the halogens the chemical reactivity decreases with increase in atomic number down the group
✓

Answer

Correct option: A.
Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens
a
$(1)$ In a period, from left to right the acidic strength increases that mean basic nature decreases.

$(2)$ In a group, from top to bottom the basic nature increases that means acidic nature decreases.

$Na, Mg$ and $Al$ are present in same period so the order of basic nature among and $Al$ is $Na> Mg > Al.$

And $\mathrm{Na}$ and $\mathrm{K}$ are from same group so basic nature of $\mathrm{K}>\mathrm{Na}$.

So the correct order of oxides

$\mathrm{Al}_{2} \mathrm{O}_{3}<\mathrm{MgO}<\mathrm{Na}_{2} \mathrm{O}<\mathrm{K}_{2} \mathrm{O}$

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