Question

Atomic Number of the elements of 3
rd
period of Modern Periodic table is listed below.

Study the data carefully and answer the questions that follow:

[5]

Period 3
elements

Na Mg Al Si P S Cl Ar

Atomic
Number

11 12 13 14 15 16 17 18
a)Arrange the above elements in decreasing order of atomic radius.Justify your answer.
b) Which will be more metallic in nature: Na or Al? Why?
c) Why is Mg2+ smaller than its corresponding atom?
d) In which group will you place sodium and phosphorus ? Why?

Answer 1

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Answer 2

Answer: HEY MATE!HERE'S YOUR ANSWER!

A) Na>Mg>Al>Si>P>S>Cl>Ar

REASON:atomic radius decreases as we move from left to right in a period.

B) Na will be more metallic in nature.

REASON:Na has only one elctron in its outermost shell(2,8,1)but Al has three electrons in its outermost shell(2,8,3).since metallic character depends on ability to lose electrons easily,Na can easily lose that one electron that Al.Also,metallic character decreases as we move from left to right in a period.

C) Mg2+ is smaller than corresponding atom i.e Mg because it has lost 2 electrons to form Mg2+ cation.Now its configuration is only (2,8) while the original configuration was (2,8,2).Mg2+  has lost its M shell but Mg still has M shell.So Mg2+ is smaller.

D)Sodium can be placed in first group because it only has one valence elctron in its outermost shell.Phosphorus can be placed in the 15th group as it has 5 electron in its outermost shell.

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Explanation: