● Emission spectra are produced when photons are emitted from atoms as excited electrons return
to a lower energy level.
● The line emission spectrum of hydrogen provides evidence for the existence of electrons in
discrete energy levels, which converge at higher energies.
Guidance
The names of the different series in the hydrogen line spectrum are not required.
● The main energy level or shell is given an integer number, n, and can hold a maximum number of
electrons, 2n2.
● A more detailed model of the atom describes the division of the main energy level into s, p, d, and
f sub-levels of successively higher energies.
● Sub-levels contain a fi xed number of orbitals, regions of space where there is a high probability of
fi nding an electron.
● Each orbital has a defi ned energy state for a given electronic confi guration and chemical
environment and can hold two electrons of opposite spin.

Description of the relationship between colour, wavelength, frequency, and energy across the
electromagnetic spectrum.
Guidance
Details of the electromagnetic spectrum are given in the IB data booklet in section 3.
● Distinction between a continuous spectrum and a line spectrum.
● Description of the emission spectrum of the hydrogen atom, including the relationships between
the lines and energy transitions to the fi rst, second, and third energy levels.
● Recognition of the shape of an s orbital and the px, py, and pz atomic orbitals.
● Application of the Aufbau principle, Hund’s rule, and the Pauli exclusion principle to write electron
confi gurations for atoms and ions up to Z = 36.
Guidance
● Full electron confi gurations (e.g. 1s22s22p63s23p4) and condensed electron confi gurations (e.g.
[Ne]3s23p4) should be covered.
● Orbital diagrams should be used to represent the character and relative energy of orbitals. ​The electron confi gurations of Cr and Cu as exceptions should be covered.

This video is introducing the energy levels of atoms. It also demonstrates why energy levels are quantised.  

The video "Energy levels - AS Quantum" explains about the energy levels in atoms. It explains how photons can transition electrons from the ground state to the an excited state. In addition, the video illustrates what happens when the excited electrons transitions back to the ground state.

Watch the video and take notes about how photons excite electrons and how electrons give up photons when they transition back to the ground state. 

Discuss the questions below by writing comments on the blog "Energy levels and emission spectrum" (link is below) 

Question: Energy levels and emission spectrum 
Look at the picture of the hydrogen line emission spectrum (figure 1) below and discuss why this emission spectra has only certain lines rather than the whole spectra with all the colours. Use the video "Energy levels - AS Quantum" and figure 2 to help you explain using scientific reasoning.

Application
How is the quantisation of energy actually visible? In what circumstance would I actually need to know about energy levels? How does this all relate to practical stuff rather than just theory? 

Watch the video and take notes about why different metal salts burn in different colours. Consider the quantisation of energy emitted. ​

Discuss why the different metal salts burn in different colours by using the theory of quantisation of energy and the information in the video "Energy levels - AS Quantum". Read your classmates comments and comment yourself on the blog post "Flame test - Application". 

The video shows how  from white light (sunlight) one  generates all of the colours of the materials that the artist is using. Those materials cause the transformation of white light to the colours that the artist want to portray. 

Task:

• Watch the video and take notes 
• Answer the following questions:

1. How does this transition occur?
2. How do we perceive this transition?
3. What happens between the art wok and art perception?

Exam questions 

​​1. What is the electron configuration of vanadium?
A.    1s2 2s2 2p6 3s2 3p6 3d2 4s3
B.    1s2 2s2 2p6 3s2 3p6 3d3 4s2
C.    1s2 2s2 2p6 3s2 3p6 3d4 4s1
D.    1s2 2s2 2p6 3s2 3p6 3d5
(Total 1 mark)

2. In the emission spectrum of hydrogen, which electronic transition would produce a line in the visible region of the electromagnetic spectrum?
A.    n = 2 →n = 1
B.    n = 3 → n = 2
C.    n = 2 → n = 3
D.    n = ∞ → n = 1
(Total 1 mark)

​3. The electron configuration of chromium can be expressed as [Ar]4sx3dy.
(i)    Explain what the square brackets around argon, [Ar], represent.
......................................................................................................................................
......................................................................................................................................
(1)
(ii)    State the values of x and y.
x: ..................................................................................................................................
y: ..................................................................................................................................
(1)
(iii)    Annotate the diagram below showing the 4s and 3d orbitals for a chromium atom using an arrow,   and  , to represent a spinning electron.





(1)
(Total 3 marks)

​4. Which describes the visible emission spectrum of hydrogen?
A.    A series of lines converging at longer wavelength
B.    A series of regularly spaced lines
C.    A series of lines converging at lower energy
D.    A series of lines converging at higher frequency
(Total 1 mark)

6. Draw and label an energy level diagram for the hydrogen atom. In your diagram show how the series of lines in the ultraviolet and visible regions of its emission spectrum are produced, clearly labelling each series.

(Total 4 marks)