3.4- ENERGY LEVELS IN ATOMS

Question 1

What are the electrons of an atom trapped by?

Answer 1

electrostatic force of attraction of the nucleus

Question 2

How do the electrons move about?

Answer 2

move about the nucleus in allowed shells/orbits, surrounding the nucleus

Question 3

What is the energy of an electron in a shell closer to the nucleus like in comparison to an electron in a shell further away?

Answer 3

electron in a shell near nucleus has less energy than electron in shell further away from nucleus

Question 4

What is an atoms ground state?

Answer 4

lowest energy state of an atom

Question 5

What happens when an atom in the ground state absorbs energy?

Answer 5

one of its electrons moves to a shell at higher energy, so atom now in excited state

Question 6

What can the excitation energy measurements be used to construct?

Answer 6

energy level diagram for the atom

Question 7

What does an energy level diagram show?

Answer 7

the allowed energy values of the atom

Question 8

What does each allowed energy of an energy level diagram correspond to?

Answer 8

certain electron configuration in the atom

Question 9

If the ionisation level is considered as the zero reference level, what would the energy levels below it be like?

Answer 9

shown as negative values

Question 10

What do gases at low pressure emit when they’re made to conduct electricity?

Answer 10

light

Question 11

What does a neon tube emit when it conducts electricity?

Answer 11

red-orange light

Question 12

What does the gas-filled tube used to measure excitation energies emit and when?

Answer 12

light when excitation occurs

Question 13

Why is light emitted when excitation occurs in a gas-filled tube?

Answer 13

happens as the atoms absorb energy due to excitation by collision, but don’t retain the absorbed energy permanently

Question 14

What is the electron configuration in an excited atom like?

Answer 14

unstable

Question 15

Why is the electron configuration in an excited atom unstable?

Answer 15

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

Question 16

What happens to the vacancy in a shell when an electron moves from it?

Answer 16

vacancy filled by an electron from an outer shell transferring to it

Question 17

What happens when the vacancy in a shell is filled by an electron from an outer shell transferring to it?

Answer 17

electron emits a photon

Question 18

What is the process of de-excitation?

Answer 18

atom moves to a lower energy level

Question 19

What is the energy of a photon emitted when an electron de-excites?

Answer 19

equal to energy lost by electron and so by atom

Question 20

Can an atom de-excite indirectly?

Answer 20

yes

Question 21

How can an atom de-excite indirectly?

Answer 21

via several energy levels if intermediate energy levels are present

Question 22

How is the energy of an emitted electron calculated?

Answer 22

energy of emitted electron hf = E1 - E2

Question 23

What can an electron in an atom do to move to an outer shell where vacancy exists?

Answer 23

absorb a photon

Question 24

What must the photon be like for it to be absorbed by an electron in an atom to move to an outer shell where vacancy exists?

Answer 24

energy of photons is exactly equal to gain in electron’s energy

Question 25

What happens if the photon energy needed by an electron in atom to move to an outer shell where vacancy is smaller or larger than the difference between the two energy levels?

Answer 25

will not be absorbed the electron

Question 26

In what ways can an atom in an excited state de-excite to ground state?

Answer 26

directly or indirectly, regardless of how excitation took place

Question 27

What can an atom absorb and emit?

Answer 27

photons of certain energies + emit photons of same/less energies

Question 28

What does the overall process of the atom exciting and de-exciting explain?

Answer 28

why certain substances fluorescence/ glow with visible light when they absorb UV radiation

Question 29

What do certain substance absorb? (fluorescence)

Answer 29

UV photons + become excited

Question 30

What does the atoms of the substance emit when they de-excite? (fluorescence)

Answer 30

emit visible photons

Question 31

What happens when the source of UV radiation is removed? (fluorescence)

Answer 31

substance stops glowing

Question 32

What is a fluorescence tube?

Answer 32

glass tube with a fluorescent coating on its inner surface

Question 33

What does the fluorescent tube contain?

Answer 33

mercury vapour

Question 34

What pressure is the mercury vapour at inside the fluorescent tube?

Answer 34

low pressure

Question 35

How does the ionisation + excitation of the mercury atoms within the fluorescent tube occur?

Answer 35

they collide with each other + with electrons in the tube

Question 36

What do the mercury atoms in the fluorescent tube emit when they de-excite?

Answer 36

UV photons, visible photons + photons of much less energy

Question 37

What happens to the UV photons emitted by the mercury atoms in the fluorescent tube?

Answer 37

UV photons absorbed by atoms of fluorescent coating

Question 38

What happens as the atoms of the fluorescent coating absorb the UV photons?

Answer 38

atoms become excited

Question 39

What do the coating atoms emit when they de-excite?

Answer 39

visible photons

Question 40

Is a florescent tube or filament lamp more efficient?

Answer 40

fluorescent tube more efficient

Question 41

How is a lot of energy wasted In a filament lamp?

Answer 41

heat energy