Unit 1 Inorganic Chemistry: Key Area 1 - Electromagnetic Radiation and Atomic Spectra

Question 1

What are the 6 forms of electromagnetic radiation?

Answer 1

• Gamma rays
• X-rays
• UV radiation
• Visible Light
• Infrared Radiation
• Radio waves

Question 2

What are the key features of Gamma Rays?

Answer 2

• Shortest wavelength (less than 0.01nm)
• Highest frequency
• Most energetic radiation
• Emitted in nuclear reactions

Question 3

What are the key features of X-rays?

Answer 3

• Wavelength (0.01-10nm)
• High frequency
• High energy region
• Emitted from superheated gas from stars etc.

Question 4

What are the key features of UV Radiation?

Answer 4

• Wavelength (10-310nm)

- Emitted by young hot stars

Question 5

What are the key features of Visible Light?

Answer 5

• Wavelength (400-700nm)
• Emitted by the sun
• Detected by eyes

Question 6

What are the key features of Infrared Radiation?

Answer 6

• Wavelength (710-1000nm)

- Emitted by the human body

Question 7

What are the key features of Radio Waves?

Answer 7

• Largest wavelength (71mm)
• Shortest frequency
• Least energetic region

Question 8

What does all electromagnetic radiation have in common?

Answer 8

All electromagnetic radiation travels at the same velocity (the speed of light in a vacuum/3x10 8ms-1).

Question 9

What is the measurement and symbol of wavelength?

Answer 9

Peak to peak/trough to trough measured in m with the symbol λ.

Question 10

What is the frequency and energy of a short wavelength?

Answer 10

High frequency and high energy.

Question 11

What is the frequency and energy of a long wavelength?

Answer 11

Low frequency and low energy.

Question 12

What is the frequency of a wave?

Answer 12

The number of waves which pass a fixed point in one unit of time.

Question 13

What is the electromagnetic equation?

Answer 13

C = f λ

Question 14

What is frequency measured in?

Answer 14

Hz or s-1

Question 15

What is known as the electromagnetic spectrum?

Answer 15

The different types of radiation arranged in order of wavelength is known as the electromagnetic spectrum.

Question 16

What are wavelengths normally expressed in?

Answer 16

Nanometers (nm)

Question 17

In what ways can electromagnetic radiation be described?

Answer 17

Electromagnetic radiation can be described as a wave (has a wavelength and frequency), and as a particle, and is said to have a dual nature..

Question 18

When electromagnetic radiation is a absorbed or emitted by matter, how does it behave and what are the emitted particles called?

Answer 18

When electromagnetic radiation is absorbed or emitted by matter it behaves like a stream of particles. These particles are known as photons.

Question 19

How many photons per second are emitted by dim light and intense light?

Answer 19

• Dim light: few photons per (s)

- Intense light: lots of photons per (s)

Question 20

When photons are emitted or absorbed, what happens to the energy?

Answer 20

When a photon is absorbed or emitted, energy is gained or lost by electrons within the substance.

Question 21

What are the equations for the energy associated with a single photon?

Answer 21

E = h f, E = hc/λ, E = LHF
L = avocados constant found on pg 23

Question 22

What is the relationship between the transfer of energy and frequency?

Answer 22

The photons in high frequency radiation can transfer greater amounts of energy than photons in low frequency radiation.

Question 23

What do photons carry?

Answer 23

A photon carries quantised energy proportional to the frequency of radiation.

Question 24

What may happen when energy is transferred to atoms?

Answer 24

When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels.

Question 25

when does an atom emit a photon of light energy?

Answer 25

An atom emits a photon of light energy when an excited electron moves from a higher energy level to a lower energy level.

Question 26

What is Bohr’s model of the atom?

Answer 26

• Electrons exist in definite energy levels.
• An atom emits a photon of light energy when an excited electron moves from a higher energy level to a lower energy level.
• When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels.
• The energy of the photon is equal to the difference between the two energy levels, and is related to frequency by E = h f.

Question 27

What provides evidence for energy levels?

Answer 27

The light energy emitted by an atom produces a spectrum that is made up of a series of lines at discrete (quantised) energy levels. This provides direct evidence for the existence of these energy levels.

Question 28

What are the principles of spectroscopy?

Answer 28

Each element in a sample produces characteristic absorption and emission spectra. These spectra can be used to identify and quantify the element.

Question 29

How does Atomic Absorption Spectroscopy (AAS) work?

Answer 29

In absorption spectroscopy, electromagnetic radiation is directed at an atomised sample. Radiation is absorbed as electrons are promoted to higher energy levels. An absorption spectrum is produced by measuring how the intensity of absorbed light varies with wavelength.

Question 30

How does emission spectroscopy?

Answer 30

In emission spectroscopy, high temperatures are used to excite the electrons within atoms. As the electrons drop to lower energy levels, photons are emitted. An emission spectrum of a sample is produced by measuring the intensity of light emitted at different wavelengths.

Question 31

How does atomic spectroscopy work?

Answer 31

In atomic spectroscopy, the concentration of an element within a sample is related to the intensity of light emitted or absorbed.

Question 32

Why are lines produced in an emission spectrum? (2)

Answer 32

• Energy is absorbed resulting in electrons being promoted to a higher energy level. (1)
• Lines produced from electrons falling to ground state emit energy corresponding to the wavelength of one of the lines. (1)