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

Question 1

What is the wavelength of a wave?

Answer 1

The distance between two crests of a wave. (measured in nanometers/ 10^-9)

Question 2

Define the frequency of a wave.

Answer 2

The number of wavelengths that pass a certain point in one second. (measured in Hertz/Hz

Question 3

What is the speed of electromagnetic radiation?

Answer 3

3x10^8 m/s

Question 4

What does the symbol L stand for?

Answer 4

Avogadro’s constant

Question 5

What does the symbol ‘c’ stand for?

Answer 5

Velocity

Question 6

What does the symbol ‘h’ stand for?

Answer 6

Planck’s constant

Question 7

When electromagnetic radiation acts more like particles than waves what are these called?

Answer 7

Photons

Question 8

What is the formula to calculate the energy carried by a photon?

Answer 8

E=hf

Question 9

How do you convert J mol^-1 to kJ mol^-1?

Answer 9

Divide by 1000

Question 10

What is the atomic emission spectrum?

Answer 10

A coloured light obtained by passing high voltage electricity through a gas tube at low pressure. You can analyse this light by passing it through a prism. This light is diffracted and a series of lines is shown. These lines are the atomic emission spectrum of an atom/ molecule

Question 11

What causes atomic emission spectra?

Answer 11

When an excited electron loses energy and jumps back down to either its ground state or a lower energy level and the lost energy is released in the form of photons. Each line corresponds to the energy given out when an excited electron moves to a lower energy state.

Question 12

What causes atomic absorption spectra?

Answer 12

When the electrons are promoted and absorption spectrum is produced by measuring what wavelengths have been absorbed by the sample. This is also specific to a particular element.

Question 13

What is the visible region of the spectrum?

Answer 13

400-700nm

Question 14

What is the ultra violet range?

Answer 14

200-400nm

Question 15

What happens when atoms absorb photons?

Answer 15

Electrons in the atom gain energy and are now in an excited state

Question 16

What happens when atoms emit photons?

Answer 16

They lose energy and return to the ground state

Question 17

What are 6 forms of electromagnetic radiation?

Answer 17

• Gamma rays
• X rays
• UV radiation
• Visible light
• Infrared radiation
• Radio waves

Question 18

What is the frequency and energy of a short wavelength?

Answer 18

High frequency and high energy

Question 19

What is the frequency and energy of a long wavelength?

Answer 19

Low frequency and low energy

Question 20

In what ways can electromagnetic radiation be described?

Answer 20

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 21

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

Answer 21

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

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 that the 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 happens 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

Why are lines produced in an emission spectrum?

Answer 26

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