1.1 Electromagnetic Radiation and Atomic Spectra

Question 1

How can electromagnetic radiation be describes and charaterised?

Answer 1

• Described in terms of waves
• Characterised in terms of wavelength and or frequency

Question 2

What is the relationship between wavelength and frequency?

Answer 2

c = fλ

Question 3

What can different types of radiation arranged in order of wavelength be known as?

Answer 3

Electromagnetic radiation

Question 4

What are wavelengths of visible light normally expressed in

Answer 4

nm (nanometers)

Question 5

Describe the duel nature of electromagnetic radiation?

Answer 5

When electromagnetic radiation is absorbed or emitted by mater it can be described as a wave and as a particle

Question 6

What are photons?

Answer 6

Particles of light emitted when electromagnetic radiation is emitted or absorbed by matter

Question 7

What happens when electromagnetic radiation is absorbed or emitted by matter?

Answer 7

It behaves like a stream of particles called photons

Question 8

What does a photon carry?

Answer 8

Quantised energy

Question 9

Explain the energy of a photon

Answer 9

it is proportional to the frequency of radiation

Question 10

What happens when a photon is absorbed or emitted?

Answer 10

energy is gained or lost by electrons within the substance

Question 11

Explain photons in high and low frequency radiation

Answer 11

• Photons in high frequency radiation can transfer greater amounts of energy
• than photons in low frequency radiation

Question 12

What is the energy associated by one single photon given by?

Answer 12

E = hf

E = hc / λ

Question 13

What is the energy associated by one mole of photons given by?

Answer 13

E = Lhf

E = Lhc / λ

Question 14

What units are energy often in?

Answer 14

KJmol^-1

Question 15

What happens when energy is transferred to atoms?

Answer 15

electrons within the atoms may be promoted to higher energy levels

Question 16

When will an atom emit a photon of light ?

Answer 16

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

Question 17

What happens when an exited electron move from a higher energy level to a lower energy level?

Answer 17

A photon of light is emitted

Question 18

What provides direct evidence for the existence of energy levels?

Answer 18

The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete energy levels

Question 19

What does each element in a sample produce?

Answer 19

Characteristic absorption and emission spectra

Question 20

What can the characteristic absorption and emission spectra of an element be used for?

Answer 20

Can be used to identify and quantify the element

Question 21

What happens in absorption spectroscopy?

Answer 21

• EM radiation is directed at an atomised sample
• Radiation is absorbed as electrons are promoted to higher energy levels

Question 22

How is an absorption spectrum produced?

Answer 22

By measuring how the intensity of absorbed light varies with wavelength

Question 23

What happens in emission spectroscopy?

Answer 23

• High temperatures are used to excited the electrons within atoms
• As the electrons drop to lower energy levels, photons are emitted

Question 24

How is an emission spectrum produced?

Answer 24

By measuring the intensity of light emitted at different wavelengths

Question 25

In atomic spectroscopy, What is the concentration of an element withing the sample related to?

Answer 25

The intensity of light emitted or absorbed