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Periodic Classification of Elements — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10SciencePeriodic Classification of Elements1 Mark
MCQ
For two statements are given $-$ one labelled Assertion $(A)$ and the other labelled Reason $(R)$. Select the correct answer to these questions from the codes $\ce{(a), (b), (c)}$ and $(d)$ as given below :
Assertion : Increasing order of metallic character is $: : \ce{P < Si < Be < Mg < Na}$
Reason : Metallic character increases along a period and decreases down a group.
  • A
    Both $A$ and $R$ are true, and $R$ is correct explanation of the assertion.
  • B
    Both $A$ and $R$ are true, but $R$ is not the correct explanation of the assertion.
  • ✓
    $A$ is true, but $R$ is false.
  • D
    $A$ is false, but $R$ is true.
✓

Answer

Correct option: C.
$A$ is true, but $R$ is false.
Elements can be arranged in different periods and groups as follows :
$\begin{matrix}\text{Period/ Group} & 1 & 2 & 13 &14&15\\2\text{nd}&-&\text{Be}&-&-&-\\3\text{rd}&\text{Na}&\text{Mg}&-&\text{Si}&\text{P}\end{matrix}$
As metallic character decreases along a period and increases down a group, so $\ce{Na}$ is the most metallic
element and $P$ is the least metallic element and among $\ce{Be}$ and $\ce{Mg, Mg}$ is more metallic. Hence, increasing order of metallic character is : $\ce{P < Si < Be < Mg < Na}.$

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