3.4 Energy Levels In Atoms

Question 1

Does an electron shell near the center of the nucleus have more or less energy than an electron further away from the nucleus

Answer 1

Has less energy

Question 2

What is the ground state of an atom

Answer 2

The lowest state of energy of an atom

Question 3

What is the excited stage

Answer 3

When an atom at ground state absorbs energy and one of its electrons moves to a shell at a higher energy

Question 4

What does each energy allowed (excitation energy) correspond to

Answer 4

A certain electron configuration in an atom

Question 5

What might the ionisation level be considered as

Answer 5

The zero reference level for energy instead of the ground state level
Energy levels below ionisation level would need to be shared as negative values

Question 6

What happens to gas at a low pressure that are made to conduct electricity

Answer 6

They emit light

Question 7

What colour is neon a metal when it conducts electricity

Answer 7

Red/orange light

Question 8

What can A gas filled tube be used to measure

Answer 8

Excitation energy

Question 9

Why is light emitted during deexcitation

Answer 9

Because the atoms absorb energy as a result of excitation by collision but they do not retain the absorbs energy permanently

Question 10

Why is the electron configuration excited atom unstable

Answer 10

Because an electron moves to an outer shell leaves a vacancy in the shell that it moves from

Question 11

What is the process of deexcitation

Answer 11

The vacancy is filled by an electron from the outer shell

when this happens the electron emitts a photon
the atom therefore moves to a lower energy level

Question 12

What is the energy of a photon released by de excitation equal to

Answer 12

The energy lost by the electron and therefore by the atom

Question 13

What is the energy of the emitted photon equal to

Answer 13

Hf = E1-E2

Question 14

What must the photon have in order for an electron in the atom to move to an outer shell where a vacancy exists

Answer 14

The energy of a photon must be exactly equal to the gain of electrons energy
In other words the photon energy must be exactly equal to the difference between the final and the initial energy of the atom


Question 15

What happens if the photons energy is smaller or larger than the difference between the two energy levels

Answer 15

It will not be absorbed by the electron

Question 16

What can an atom in an excited state deexcite directly or indirectly to ground state regardless of

Answer 16

How the excitation took place

Question 17

An atom can absorb photons of certain energies and then emitt photons of

Answer 17

Same or less energy

Question 18

why do certain substances fluoresce or glow with visible light when they absorb UV radiation

Answer 18

Atoms in the substance absorb ultraviolet photons and become excited

when the atoms de-excite they emit visible light photons

Question 19

what would happen if you removed UV radiation from a florescent object

Answer 19

It would stop glowing

Question 20

what is a fluorescent tube

Answer 20

A glass tube with fluorescent coating on its inner surface

the tube contains mercury at a Low pressure

Question 21

why does a fluorescent tube emit visable light (steps)

Answer 21

• ionisation and excitation of the mercury atoms occurs as they collide with each other and the electrons in the tube
• the mercury atoms emit ultraviolet photons as well as visible photons and photons of much less energy
• the ultraviolet photons are absorbed by the atoms of the fluorescent coating causing there excitation
• the coating atoms de excite in steps and emit visible light photons

Question 22

why is a fluorescent tube much more officiant than filament lamp

Answer 22

a typical 100W filament lamp releases about 10-15W of light energy
the rest of the energy is lost to heat

fluorescent tube can produce the same light output with no kore than a few watts of power wasted as heat

Question 23

what does a fluorescent tube have at each end

Answer 23

a filament electrode

Question 24

why is a stater unit necessary in a fluorescent tube

Answer 24

because the mains voltage is too small to ionise the vapour in the tubes when the electrodes are cold

Question 25

what happens when the tube is first switched on

Answer 25

the gas (argon) in the starter switch unit conducts and heats a bimetallic strip making it bend so the switch closes

the current through the starter unit increases enough to heat the filament electrodes

Question 26

what happens when the bimetallic strip closes

Answer 26

the gas in the starter unit stops conducting and so the bimetallic strip cools and the switch opens

the mains voltage now acts between the 2 electrodes which are now hot enough for the ionisation of the gas to occur

Question 27

what is wasted in a filament bulb and a low energy bulb when it emits about 15W of light

Answer 27

emits 75W

efficient wastes 5W