What are the different types of JC Chemistry tuition classes available at your centre?

We have 3 modes of learning for students to choose from: weekly physical classes at Bishan; weekly online lessons via Zoom; and on-demand video lessons.

Are you the only Chemistry tutor conducting the classes or do you engage other tutors to do that?

Please be rest assured that I conduct all my classes personally and I do not engage other tutors to teach at my centre.

What is your class size at Bishan?

Usually the class size is around 10 to 12 students. Max class size is 16 pax.

Is there makeup lesson if I miss a class?

Yes makeup lesson is available in the same week subject to availability. If makeup class is not possible, the student can view the recorded video lessons at Google Classroom.

Do you have trial lesson available? How much is it?

Yes we do. Fees for trial lesson are for Bishan class and for Zoom online class.

Does your centre offer O Level chemistry tuition? Do you teach IB / IP chemistry tuition? How about H1 Chemistry?

Chemistry Guru specialises in H2 Chemistry for JC1 and JC2 or IP Year 5 and IP Year 6 students only. Find out all the information about A Level H2 Chemistry and the detailed comparison between H1 and H2 Chemistry. We do not conduct lessons for H1 Chemistry, O Level Chemistry, IB Chemistry or IP Chemistry at IP Year 3 and IP Year 4.

High Spin and Low Spin Complexes

Transition metal complexes can exist as high spin or low spin depending on the strength of the ligands.

Let's understand how the strength of ligands affect the spin of the complex.

This concept involving high spin and low spin complexes is not in A Level Chemistry syllabus but has appeared in some Prelim questions.

1. Gaseous Fe(III) cation

The electronic configuration for Fe³⁺ is given as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵

We can also determine the electron in box diagram for 3d subshell.

high spin and low spin complexes electronic config of 3d subshell in FeIII gas

Notice there are 5 unpaired electrons in 3d subshell for Fe³⁺.

2. Hexaaquairon(III) complex

Since oxidation state of iron is still +3, there are still 5 electrons in 3d subshell in [Fe(H₂O)₆]³⁺ complex.

In a complex the ligands will interact with the d orbitals to different extent depending on the shape of the complex.

Therefore the d orbitals that interact more with the ligands will have a higher d* energy level, while the d orbitals that interact less will have a lower d energy level.

This is known as d-d* orbital splitting.

For octahedral complexes, the splitting pattern is 2 orbitals at higher d* level and 3 orbitals at lower d level.

Water is a weak ligand and the energy gap between d to d* level is small.

Hence the d electrons will ignore the small energy difference and be filled in the same way as in gaseous Fe³⁺ cation, where electrons will occupy orbitals singly and with parallel spins.

high spin and low spin complexes electronic config of 3d subshell in high spin hexaaquaironIII complex

Notice there are 5 unpaired electrons, hence hexaaquairon(III) complex is considered a high spin complex.

3. Hexacyanoferrate(III) complex

CN^- is a strong ligand and will cause the energy gap between d to d* level to be larger.

It requires too much energy to put the d electrons at the higher d* level, so electrons will pair up at the lower d level first.

high spin and low spin complexes electronic config of 3d subshell in low spin hexacyanoferrateIII complex

Notice there is now only 1 unpaired electron, hence hexacyanoferrate(III) complex is considered a low spin complex.

Comparing both high spin and low spin complexes:

- a weak ligand such as H₂O will cause a smaller d-d* energy gap and tend to form high spin complexes
- a strong ligand such as CN^- will cause a larger d-d* energy gap and tend to form low spin complexes

high spin and low spin complexes compare high spin and low spin complexes