Transition Metals part 2

Question 1

What happens to electrons in the transition metals to cause them to form coloured compounds

Answer 1

d electrons move from ground state to excited state when light is absorbed

Question 2

Show the equation for the change in energy between the ground state and the excited state of the electrons

Answer 2

∆E = hν = hc/λ
where
delta E= change in energy
h= planck’s constant
v= frequency of light absorbed (Hz)
c= speed of light
λ = wavelength of light absorbed (m)

Question 3

Name things the size of ∆E is dependent on

Answer 3

• the central metal ion and its oxidation state
• the type of ligand
• coordination number

Question 4

What type of apparatus can be used to determine what transition metal is present in a compound

Answer 4

Colorimeter

Question 5

Explain how colorimetry can be used to identify transition metal ions in a solution

Answer 5

Light source emits white light
Which is passed through a colour filter
Shined at sample
Colorimter measures amount of light absorbed

More concentrated solutions absorb more light - this can be used to determine concentrations of ions in solution

Compare absorption to known concentrations using calibration graph

Question 6

What is the energy gap

Answer 6

When a transition metal ion is unbonded all the electrons are all on the same energy level
When the ion bonds with ligands some of the d subshell electrons move into an elevated shell so there is a gap in energy between the two levels

Question 7

What does the size of the frequency of light absorbed depend on

Answer 7

∆E

The greater ∆E, the higher the frequency of light absorbed

Question 8

Explain absorption/reflection of light in terms of what colours of transition metals we observe

Answer 8

Any frequencies of light nor absorbed are reflected or transmitted
On the colour wheel the colour absorbed is opposite the colour observed (reflected)

Question 9

Colour of V2+

Answer 9

Violet

Question 10

Colour of V3+

Answer 10

Green

Question 11

Colour of [VO]2+

Answer 11

Blue

Question 12

Colour of [VO2]+

Answer 12

yellow