Question

Elements having valency 1 are
A) always metals
B) always non-metals
C)always metalloids
D)either metals or non - metals.

Give reasons for your answer .

Answer 1

Elements having valency 1 are Metals or Non-metals.
So Option D- is the correct answer.
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Reason:
Elements Having valency are placed in First group of periodic table. Which are known as Alkali Metals .
Examples are Sodium, potassium etc...
Hydrogen has some exceptions as
Alkali metals .
Hydrogen which has valency 1 resembles Halogens like Fluorine, chlorine which can exist as diatomic molecule. Hence it can be nonmetal.
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Answer 2

Elements having valency 1 can either be metal or non metal .

So option D is correct

Reason
Suppose we take example of alkali metals.
Their electronic configuration will always end on ns1
Let take Sodium metal as an example for better clarification
Electronic configuration of Sodium is 1s2,2s2,2p6,3s1
So sodium loses one electron from the s orbital and become positive univalent, therefore having a valency of 1.

Now let's talk about group 17 elements namely Halogens
The electronic configuration of any halogen ends with np5.
Any halogen- Chlorine(say)
The electronic configuration of chlorine is 1s2,2s2,2p6,3s2,3p5
So chlorine atom gains one electron to form a negative univalent ion, therefore having a valency of 1 .
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So metals and non metals can share the valency of 1