Spectroscopy

Question 1

What is spectroscopy?

Answer 1

The study of the interaction of radiation with matter

Question 2

Describe atomic absorption spectroscopy?

Answer 2

Electrons can gain energy by the absorption of energy in a photon which causes electronic transition

Question 3

What happens in an electronic transition?

Answer 3

The electrons are promoted to a higher energy level

Question 4

What does the energy of the absorbed photon correspond to?

Answer 4

The energy difference between the upper and lower energy levels

Question 5

What will the absorbed photon have?

Answer 5

A specific frequency and wavelength I.e. A specific energy

Question 6

What happens to the sample during atomic absorption spectroscopy?

Answer 6

The sample is vaporised and placed in the path of em radiation (white light/ all wavelengths).
Incident light > sample > transmitted light
(All wavelength). (Wavelengths missing)
Absorption by the sample will remove some of the photons from the em radiation (the energy is used to promote electrons to higher energy levels)

Question 7

What does an absorption spectrum measure?

Answer 7

How a samples transition of light varies with wavelength

Question 8

What does an atomic absorption spectrum appear as?

Answer 8

Dark lines on a continuous spectrum

Question 9

What do the dark lines correspond to?

Answer 9

Wavelengths of light that have been absorbed by the sample

Question 10

What are electronically excited states of ATOMS generated by?

Answer 10

High voltage electric discharges through the sample, or by high temperatures

Question 11

Describe atomic emission spectroscopy ?

Answer 11

The electrons lose their excitation energy by returning to the ground stage. This is accompanied by the emission of a photon

Question 12

What does the emitted photon have?

Answer 12

A specific frequency

Question 13

If each electronic transmission has a specific energy value, what does this mean for the emission of electromagnetic radiation?

Answer 13

It has a specific frequency and wavelength

Question 14

What does a typical emission spectra consist of ?

Answer 14

A series of coloured line on a dark background

Question 15

What does each line correspond to ?

Answer 15

A specific electronic transition and therefore frequency

Question 16

What does the emission spectrum of hydrogen consist of?

Answer 16

A series of lines in different regions of the em spectrum

Question 17

What do the lines in the emission spectrum of hydrogen arise from?

Answer 17

Many transitons from upper energy levels to lower energy levels

Question 18

What is absorption and emission spectroscopy used to do?

Answer 18

Identify and quantify the elements present in a sample

Question 19

What does each element produce?

Answer 19

A characteristic absorption and emission spectrum that an be used to identify the element

Question 20

What does the intensity of the lone provide?

Answer 20

A measure of the quantity of an element which may be present in a sample

Question 21

What happens to the lines in an emission spectrum at high energy end of the spectrum ?

Answer 21

The lines converge

Question 22

Why does the convergence limit arise?

Answer 22

Because energy levels in an atom get closer together with increasing distance from the nucleus

Question 23

What is the convergence limit in an emission spectrum?

Answer 23

The point where the electron falls from the highest energy level to the ground state

Question 24

What is the energy produced by this transition approximately equal to?

Answer 24

The energy required to remove the electron from the atom I.e. The ionisation energy