Question

c. Non metal with valency 1.​

Answer 1

The only non-metal in period 3 with valency 1 is chlorine [Cl].

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Answer 2

Answer:

Great question, Thanks for asking.

The Family of Non-Metals having one valence electron are known as Halogens Family.

⇒ Group 17 Also called halogens family is the family of Non-metals having       one valence Electron.

⇒ They are highly reactive non-metals

⇒ They are one electron short to complete their octet and to become stable.

⇒ Basically high electronegative elements are known as Non-metals.

Halogens Family (Group -17) Electronic configuration 

Florine (F⁹) -------→ Electronic configuration⇒[He]2s²,2p⁵

Chlorine (Cl¹⁷)----→ Electronic configuration⇒[Ne]3s²,3p⁵

Bromine(Br³⁵)----→ Electronic configuration⇒[Ar]3d¹⁰4s²,4p⁵

Iodine(I⁵³)---------→ Electronic configuration⇒[Kr]4d¹⁰,5s²,5p⁵

Astatine (As⁸⁵)--→ Electronic configuration⇒[Xe]4f¹⁴,5d¹⁰,6s²,6p⁵

Hence  clearly mention here , All non-metals having one valence electrons belongs to Halogens family.

Explanation:

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