Element having variable valency 1 and 3?

1 Answer
Jul 10, 2017

Answer:

Thallium and gold have valencies of 1 and 3.

Explanation:

Thallium

Thallium is about 170 times as abundant as gold in the Earth's crust.

The electron configuration of thallium is #"[Xe] 6s"^2 4"f"^14 "5d"^10 "6p"#.

It is easy to remove the #"6p"# electron and form #"Tl"^"+"#.

The #"6s"# subshell contains the next-most easily removed electrons.

Removal of these electrons gives #"Tl"^"3+"# with electron configuration #"[Xe] 4"f^14 "5d"^10#.

Thus, some common compounds of thallium are:

  • thallium(I) sulfide #"Tl"_2"S"#,
  • thallium(I) sulfate #"Tl"_2"SO"_4#
  • thallium(III) fluoride #"TlF"_3#
  • thallium(III) oxide #"Tl"_2"O"_3#

Gold

The electron configuration of gold is #"[Xe] 6s 4"f^14 "5d"^10#.

It is easy to remove the #"6s"# electron and form #"Au"^"+"#.

The #"5d"# subshell contains the next-most easily removed electrons.

Another common state of gold is #"Au"^"3+"# with electron configuration #"[Xe] 4"f^14 "5d"^8#.

Thus, the most common compounds of gold are

  • gold(I) chloride #"AuCl"#
  • gold(III) chloride #"AuCl"_3#
  • chlorauric acid #"HAuCl"_4#

Here's a table giving the most common oxidation numbers of the elements in their compounds.

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