15.1.3 - The origin of colour in complexes

Question 1

What is the colour of metal ions with completely filled 3d energy levels?

Answer 1

Colourless

Question 2

What happens to the 3d sub shell?

Answer 2

They split into different energy levels.

Question 3

What happens to electrons in the ground state in a 3d sub shell?

Answer 3

They absorb energy from the visible spectrum.
Moves to a higher energy level.
This is called excitation.

Question 4

What does the amount of energy an electron from the ground state absorbs depend on?

Answer 4

The difference in energy between the two energy levels.

Question 5

What does a small difference in energy between the split 3d sub shell result in?

Answer 5

a low frequency of radiation is absorbed.

Question 6

What colour will be transmitted if a low frequency of visible light is absorbed?

Answer 6

Blue.

Low frequency absorbed = red light.
This has been removed from the visible light spectrum therefore we see blue (the opposite colour)

Question 7

hexaaquachromium(III) complex is coloured.
Explain why.

Answer 7

Water ligands causes d orbitals to split.
Light energy absorbed to promote electrons.
Complementary colour is transmitted.