Bohr Model, Energy Level & DeBroglie

Question 1

What causes chemical reactions?

Answer 1

Changes in electron structure

Question 2

What causes change in electron structure?

Answer 2

Interactions with light and/or electromagnetic radiation

Question 3

What is electromagnetic radiation?

Answer 3

Any kind of radiation from the electromagnetic spectrum (Gamma, X-Ray, infra-red etc)

Question 4

How can light be used to investigate electron structure?

Answer 4

1) You can add electrical energy to a vaporized sample (Investigate lights) (Emission spectra)

2) Shine full spectrum of light at a vaporized sample (Look for absorption of light) (Absorbtion Spectra)

Question 5

Solar absorption spectrum

Answer 5

• Dark lines show where light absorbed
• Frequencies absorbed characteristics of certain elements
• Identifies elements in suns atmosphere

Question 6

What is emission spectra?

Answer 6

Adding energy to atoms resulting in an emission of light

Question 7

What is absorption spectra?

Answer 7

Shining light through a vaporised element, resulting in absorption of some wavelengths of light

Question 8

Electron excitation

Answer 8

When a bound electron is transferred to a more energetic energy state

Question 9

Electron relaxation

Answer 9

When an electron in an excited state drops to a lower energy state

Question 10

Photon absorbtion

Answer 10

When a photon loses it’s energy to an atomic electron which is then emitted from an atom

Question 11

Photon emission

Answer 11

When an electron drops to a lower energy state the atom emits a photon

Question 12

What is an electron energy level?

Answer 12

Reqions around the nucleus of an atom where electrons may be found

Question 13

Whats a ground sate for an atom?

Answer 13

Its the lowest energy state for an atom, electrons can’t move to a lower orbital

Question 14

Absorption and emission spectra

Answer 14

• Spectral lines indicate change in energy values for electron energies in an atom
• Higher energy photons correspond ( Shorter wavelengths)

Question 15

What is lyman series

Answer 15

Transitions from higher energy orbits to the lowest energy orbit available (visible series; Ultra-violet)

Question 16

What is paschen series?

Answer 16

Transitions from higher energy orbits to the orbit n=3 (Infra-red)

Question 17

What is balmer series

Answer 17

Transitions from higher energy orbits to the orbit n=2 (visible series)

Question 18

What is pfund series?

Answer 18

Transitions from higher energy orbits to the orbits n=5

Question 19

What is brackett series?

Answer 19

Transitions from higher energy orbits to the orbit n=4

Question 20

Rydbergs formula

Answer 20

Calculates the wavelength of a spectral line in many chemical elements

Question 21

Bohr’s model

Answer 21

• atoms have certain energy levels
• Atom doesn’t radiate energy while its in a stationary phase
• Atom changes to another stationary state only by absorbing or emitting a photon
• Energy of a photon equals the difference in the energies of the two states

Question 22

What are the limitations of Bohr’s model?

Answer 22

• Fails for multi electron systems; only works for single electron systems
• No explanation for why there are allowed orbits

Question 23

What is Z?

Answer 23

Charge of the nucleus, +1 for Hydrogen

Question 24

What does the energy lost by an atom correspond to?

Answer 24

Corresponds to the energy of a released photon (conservation of energy)

Question 25

Conservation of energy

Answer 25

• Applies to both atom and photon
• States energy cannot be created nor destroyed; only converted from one energy form to another

Question 26

What was DeBroglies hypothesis?

Answer 26

• Proposed if energy is particle like, matter is wave like
• Electrons only have certain allowable frequencies if they have wave like motion in orbits at fixed distances from nucleus
• His equation can find the wavelength of any particle mass

Question 27

What is P?

Answer 27

P= momentum which is inversely proportional to wavelength

Question 28

Whats the wave concept for electrons?

Answer 28

• Constructive & destructive inference
• Allowed orbits = constructive inference
• Forbidden orbits will self destruct
• Allowed orbits correspond to complete wavelengths

Question 29

What are the consequences of electron wave?

Answer 29

• Location of wave like particle is imprecise
• Heisenberg uncertainty principle; cannot know both precision and momentum with certainty (If one is known accurately the other is imprecisely)

Question 30

Uncertainty principle

Answer 30

Single plane wave - will have precise energy and momentum; position of electron is infinite

Wave packett - position of electron is localized from adding different waves; energy and momentum now imprecise