Electromagnetic spectrum

Question 1

what speed does electromagnetic spectrum travels?

Answer 1

3 *10 ^8

Question 2

the wavelength of each wave length

Answer 2

10^3
10^-2
10^-5
0.5 * 10^ -6
10^-8
10^ -10
10^ -12

Question 3

Radio waves:

Answer 3

When placed inside a magnetic field, the nuclei of some atoms can spin in two (or more) directions, let’s say ‘up’ and ‘down’. The energy difference between these two states is similar to that of a radio-wave photon,

Question 4

NMR and MRI imaging.

Answer 4

so radio waves can make nuclei flip spin from up to down, or vice versa.

Question 5

Microwaves:

Answer 5

The energy of microwaves is enough to make molecules rotate.

Question 6

rotational spectroscopy, and of microwave ovens

Answer 6

(the spinning water molecules bash into neighbouring molecules and heat them up).

Question 7

Infrared:.

Answer 7

The energy of IR is now enough to make molecules vibrate. This is the basis of vibrational spectroscopy

Question 8

Visible light:

Answer 8

In large conjugated molecules (e.g. carotene, chlorophyll, heme, and azodyes) the electronic energy levels are close together. Visible light has enough energy to excite electrons, making these molecules colourful.

Question 9

Ultraviolet:

Answer 9

The energy of UV is now so great it can excite electrons even in small molecules where the separation between electronic levels is large. This is the basis for UV-vis spectroscopy. In the deep UV it can even break chemical bonds and initiate chemical reactions. In biological systems, this can damage the organism (e.g. sunburn).

Question 10

X-rays:

Answer 10

The energy of X-rays is now so large that it can eject core electrons from atoms. This is the basis for surface analysis methods like XPS.

Question 11

EM definitation

Answer 11

a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light

Question 12

characteristics of EM

Answer 12

Radio more like waves
gamma more like particle

Question 13

what is a photon

Answer 13

A photon is an elementary particle that is a quantum of the electromagnetic field

Question 14

c

Answer 14

3 x 10 8

Question 15

h plank

Answer 15

6.63 x 10 -34

Question 16

v

Answer 16

frequency

Question 17

c

Answer 17

v fancy V

Question 18

energy

Answer 18

h v

Question 19

energy

Answer 19

hc/ wavelength

Question 20

nano

Answer 20

x 10 9

Question 21

radio

Answer 21

2+ nuclei flip

Question 22

microwave

Answer 22

molecule rotation

Question 23

IR

Answer 23

Bond vibrates

Question 24

UV

Answer 24

valence electron excited. large + small molecules. photon release when back to normal

Question 25

light

Answer 25

valence electron excite photon light emitted. large molecules

Question 26

x rays

Answer 26

eject core electrons

Question 27

ground state

Answer 27

electrons lowest energy level

Question 28

quanta

Answer 28

it is discrete bundles energy levels in proportional to the frequency of the radiation

Question 29

energy

Answer 29

it cannot exist between two levels

Question 30

how to raise energy levels in electrons

Answer 30

put in a photon

Question 31

what happens

Answer 31

it will move up a energy level

Question 32

emisson spectra

Answer 32

if you place a wavelength in a gas, some of the wavelengths will be absorbed (photon). this will produce emissions in the spectra and black lines. specific elements have individual spectra

Question 33

energy levels

Answer 33

is is always negative once it is positive you will say it is ionised

Question 34

other spectra

Answer 34

electron absorb photon
release photon
specific colour in line

Question 35

CO2

Answer 35

absorbs in the IR and warms the atmosphere – the Greenhouse effect.

Question 36

Ozone

Answer 36

absorbs UV light but not visible light – the ozone layer allows visible sunlight through to the planet surface, but protects it from damaging UV.

Question 37

NMR, UV/vis and IR spectroscopy all

Answer 37

depend on energy quantisation and exploit different types of molecular energy levels (nuclear, electronic and vibrational).

Question 38

Etotal =

Answer 38

Etrans + Erot + Evib + Eelec

Question 39

Thus, molecules

Answer 39

have translational, rotational, vibrational and electronic energy levels

Question 40

,molecule energy

Answer 40

each of which are independent of the others.

Question 41

Molecules can only exist in certain discrete energy states. They can:

Answer 41

Translate
Rotate
Vibrate
and their electrons can change energy.

Question 42

Translational energy levels:

Answer 42

if a molecule is in a container of macroscopic size (e.g. this room) translational energy levels are so close together they seem continuous.

Question 43

Rotational energy levels:

Answer 43

separated by ~10-23 J (~0.006 kJ mol-1)

Question 44

Rotational energy levels:

Answer 44

separated by ~10-23 J (~0.006 kJ mol-1) value 1

Question 45

Vibrational energy levels:

Answer 45

separated by ~10-20 J (~6 kJ mol-1)
1000

Question 46

Electronic energy levels:

Answer 46

separated by ~10-18 J (~600 kJ mol-1)

100,000

Question 47

that atoms do not have bonds,

Answer 47

so they cannot rotate or vibrate

Question 48

Each electronic level has

Answer 48

a set of its own vibrational levels…

Question 49

…and each vibrational level has

Answer 49

a set of its own rotational levels.

Question 50

continuous spectra (the sun)

Answer 50

continuous means that there are no gasps in wavelength

Question 51

how to produce continuous spectra

Answer 51

hot/ dense gas — slit — prism detection

Question 52

emission detection

Answer 52

hot gas of an element
electrons are excited and absorb the heat/ current
it goes through a slit
pass prism
detects wavelength that have been aborbed

Question 53

Absorption Spectrum:

Answer 53

hot gas
pass through cold gas - it will absorb photon + energy
it will appear as dark lines

Question 54

why is the sun not continuous spectra

Answer 54

because the cooler atmosphetre

Question 55

how do we know the sun elements

Answer 55

In 1814, Joseph Fraunhofer studied the dark absorption lines in the spectrum from the Sun. The wavelengths of these lines were identical to those from emission spectra measured on Earth from elements such as sodium, hydrogen, etc. This allowed scientists to work out the composition of the Sun’s atmosphere 93 million miles away!
But there were some lines in the spectrum that had never been seen before on Earth

Question 56

emission

Answer 56

it loses photon

Question 57

absorption

Answer 57

it gains photon

Question 58

modern spectra

Answer 58

sample —– light ——- diffraction grating ——– iris——– detector