transition metal color

[nartnad]

(Destroyer Question)

"An ionic solid gave a blue color. Which solid is most likely?"

I narrowed it down to two choices, which both have transition metals:

- AgCl or CuSO4

Why is the answer CuSO4?

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[bbwreckerz04]

Its because AgCl precipitates

 

[navneetdh]

i dunno how or why i know this but i think somewhere long time ago i learnt Cu gives blue color.

So when i see blue without even looking at choices i know it has to be something with copper.

 

[nartnad]

so im under the impression that CuSO4 is soluble. Im pretty confused now. If AgCl is INSOLUBLE and CuSO4 is SOLUBLE, how is CuSO4 giving off a color as a solid, and why is AgCl not giving off a color?

 

[sixkiller]

Its because AgCl precipitates

AgCl is white...cuprric sulfate aqueous solution is light blue.

cuprric sulfate is the correct solution because it has a partially filled d subshell.

Silver is 5s1 4d10

Thus, the silver ion is 4d10 giving it a pseudo noble gas configuration. Since the d subshell is completely filled it is colorless.

Copper is 4s1 3d10, thus, Cu++ is 3d9 giving it a partially filled d subshell.

The key is to understand WHY transition metals give color; this is due to partially filled d subshells. Partially filled d subshells have energetically non-equivalent d ORBITALS.

Visible light can excite a d electron to a slightly higher energy d orbital; when it returns to the "ground state" visible light is given off.

It's a bit more complicated than that, but that's the basic jist of it.

For such problems, the key is to examine the d subshell; ask yourself, is the d subshell partially filled or does the ion have a pseudo noble gas configuration.

Another example involves cuprrous salts. PURE cuprrous salts should be colorless (white). In actuality, cuprrous salts appear greenish due cuprric impurities....

 

[sixkiller]

so im under the impression that CuSO4 is soluble. Im pretty confused now. If AgCl is INSOLUBLE and CuSO4 is SOLUBLE, how is CuSO4 giving off a color as a solid, and why is AgCl not giving off a color?

Unfortunately, that is what happens when you just memorize the rule....ie "transition metals give color."

The better approach to such problems is to examine the d-subshell.

 

[ZH1988]

(Destroyer Question)

"An ionic solid gave a blue color. Which solid is most likely?"

I narrowed it down to two choices, which both have transition metals:

- AgCl or CuSO4

Why is the answer CuSO4?

its defientaly CuSO4, because when Cu is oxidized it to Cu2+ ion, which means that the electrons now present can transition between different energy states which leads the ion to absorb light energy giving it that blue color

 

[nartnad]

AgCl is white...cuprric sulfate aqueous solution is light blue.

cuprric sulfate is the correct solution because it has a partially filled d subshell.

Silver is 5s1 4d10

Thus, the silver ion is 4d10 giving it a pseudo noble gas configuration. Since the d subshell is completely filled it is colorless.

Copper is 4s1 3d10, thus, Cu++ is 3d9 giving it a partially filled d subshell.

The key is to understand WHY transition metals give color; this is due to partially filled d subshells. Partially filled d subshells have energetically non-equivalent d ORBITALS.

Visible light can excite a d electron to a slightly higher energy d orbital; when it returns to the "ground state" visible light is given off.

It's a bit more complicated than that, but that's the basic jist of it.

For such problems, the key is to examine the d subshell; ask yourself, is the d subshell partially filled or does the ion have a pseudo noble gas configuration.

Another example involves cuprrous salts. PURE cuprrous salts should be colorless (white). In actuality, cuprrous salts appear greenish due cuprric impurities....

great explanation, thanks.