Unit 1 - Electromagnetic Radiation and Atomic Spectra

Question 1

c=fλ

Answer 1

velocity = frequency x wavelength

Question 2

velocity

Answer 2

symbol- C
speed of light 3x10^8
units- ms^-1

Question 3

wavelength

Answer 3

symbol- λ
distance between wave crest to wave crest
units- m or nm

Question 4

frequency

Answer 4

symbol- f
number of waves per second
units- Hz

Question 5

electromagnetic spectrum

Answer 5

Gamma
X rays
UV
Visible
Infra-red
Microwaves
Radio

Question 6

Electromagnetic Radiation

Answer 6

• can be described as a wave and as a particle, and is said to have a dual nature
• when absorbed or emitted by matter it behaves like a stream of particles, these particles are known as photons

Question 7

Photons

Answer 7

• when absorbed or emitted, energy is gained or lost by electrons within the substance
• photons in high frequency radiation can transfer greater amounts of energy than photons in low frequency radiation

Question 8

energy associated with a single photon is given by

Answer 8

E=hf or E=hc/λ

Question 9

energy associated with one mole of photons is given by

Answer 9

E=Lhf or E=Lhc/λ

Question 10

planck’s constant

Answer 10

symbol- h
6.63x10^-34

Question 11

avogradro’s constant

Answer 11

symbol- L
6.02x10^23

Question 12

Energy transferred to atoms

Answer 12

electrons within the atoms may be promoted to higher energy levels

Question 13

when does an atom emit a photon of light energy

Answer 13

when an excited electron moves from a higher energy level to a lower energy level

Question 14

light energy emitted by an atom produces

Answer 14

a spectrum that is made up of a series of lines at discrete energy levels. this provides direct evidence for the existence of these energy levels

Question 15

what can be used to identify and quantify an element

Answer 15

each element in a sample produces characteristic absorption and emission spectra

Question 16

Absorption Spectroscopy

Answer 16

electromagnetic radiation is directed at an atomised sample. radiation is absorbed as electrons are promoted to higher energy levels

Question 17

absorption spectrum

Answer 17

produced by measuring how the intensity of light varies with wavelength

Question 18

Emission spectroscopy

Answer 18

high temperatures are used to excite the electrons within atoms. as the electrons drop to lower levels, photons are emitted

Question 19

emission spectrum

Answer 19

is produced by measuring the intensity of light emitted at different wavelengths