ic4.7.4 spectroscopy © oxford university press 2011 spectroscopy lq: how can spectroscopy be used...

IC4.7.4 Spectroscopy

© Oxford University Press 2011

Spectroscopy

LQ: How can spectroscopy be used to identify unknown elements in a

compound?



learning outcomes…..

• MUST:• Recognise that elements have distinctive line

spectrum (B)• SHOULD: • Identify unknown elements from line spectrum

(A)• COULD:• Explain how spectroscopy has discovered new

elements (A*)



• https://www.youtube.com/watch?v=1EXr_L7Ojqg• https://www.youtube.com/watch?v=jJvS4uc4TbU



Rainbows are spectra made as sunlight

passes through raindrops.

Sunlight splits up into the various

colours of light it is made from.



Isaac Newton passed white light through

a prism. It split into the colours of the

rainbow.



• All atoms give off light when heated, although sometimes this light is not visible to the human eye.

• Each element has its own distinctive line spectrum.

• This technique is known as spectroscopy.• Some examples of what line spectra look like are

shown here



Flame tests and line spectra

Elements give off a characteristic colour in a flame test.

A spectroscope allows that light to be analysed.

Different elements have different line spectra.

Sodium flame test

Line spectrum of sodium.



• Scientists have used line spectra to discover new elements.

• In fact, the discovery of some elements, such as rubidium and caesium, was not possible until the development of spectroscopy



Modern spectroscopy

Modern spectroscopy is used

in laboratories to identify

unknown chemicals…

…and in space to find out

more about stars, planets and

galaxies.



1. When they are heated, some elements emit distinctive ____________, for example– lithium ____;– sodium ____________________;– potassium _____.

2. The light emitted from an element gives…

3. The study of spectra has helped chemists to…

4. The discovery of some elements depended on…

C

D

19 აპრი19 აპრი, 202ლი, 202ლი

33Flame colours and spectraFlame colours and spectra

discover new elements (e.g. helium).

the development of new practical techniques (for example spectroscopy).

a characteristic line spectrum.

flame colours

red(street lamp) yellow

lilac

© Class Leading Ltd. 2013. Permission granted for non-commercial educational use provided that this copyright notice is included.



• Example on board

1.How can you tell that the unknown sample contains sodium?

2.How can you tell that the unknown sample does not contain potassium?

3.How can you tell that the unknown sample contains elements other than sodium?

ic4.7.4 spectroscopy © oxford university press 2011 spectroscopy lq: how can spectroscopy be used...

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