Chapter 40

Question 1

Electron Transitions (photon radiation)

Answer 1

Question 2

Pauli Exclusion Principle

Answer 2

1. A very important physics principle forbids any two electrons to occupy the same quantum state. This is called the Pauli principle.
2. Each electron must occupy a unique state defined by a unique set of quantum numbers:

Question 3

Why does orbitals do not fill up in the expected order according to energy levels

Answer 3

This is because (for example) the 3𝑑^6 4𝑠^2 configuration results in a lower energy state for the atom than 3𝑑^8

Question 4

Total energy of an electron on shell n:

Answer 4

Question 5

When doesnt this equation apply

Answer 5

For 𝑍>1, because of electron shielding.

Question 6

For 𝑍>1 what equation do we use to calulate energy in electron shell

Answer 6

Question 7

The effective charge is equal to the

Answer 7

atomic number (all the protons) minus the shielding effect, 𝑆.
𝑄=𝑍−𝑆

Question 8

K_𝛼 electron transitions energy of the emitted photon is given by:

Answer 8

Question 9

𝐿_𝛼 transitions the energy of the emitted photon is given by:

Answer 9

Question 10

Electron tranistion summary

Answer 10

Question 11

Electron tranistion summary

Answer 11

Question 12

Moseley Equation

Answer 12

Question 13

Moseley Equation

Answer 13

Question 14

Three possible ways to obtain EM radiation from atoms

Answer 14

1. Excitation → De-excitation of electrons
2. Knock an electron out of orbit
3. Bremsstrahlung

Question 15

Excitation → De-excitation of electrons

Answer 15

shine light on the material, or heat the material, thereby causing the electrons to jump to higher energy levels. Once the energy source is removed, the electrons will de-excite (they always seek to be in the lowest energy state) and emit radiation/photons

Question 16

Knock an electron out of orbit

Answer 16

direct a beam of electrons at an atom. Some electrons will be knocked out of orbit, leaving “holes”. Electrons in higher energy levels will move to these lower energy levels (they always seek to be in the lowest energy state) and emit radiation/photons.

Question 17

Brehmsstrahlung

Answer 17

An accelerating electron emits radiation (Larmor Radiation)

When an electron approaches the negatively charged “electron cloud” of an atom it slows down (it brakes!). During this deceleration it emits radiation

Therefore:
1. Small acceleration ⇒ low energy radiation
2. Large acceleration ⇒ high energy radiation

Question 18

literally thousands of applications:

Answer 18

Laser cutters (e.g. cuts car frames)
Fibre optics
CD/DVD player
Sensitive measuring devices

Question 19

Why are lasers so useful

Answer 19

1. Monochromatic
2. Coherent
3. Directional

Question 20

Three important processes of lasers

Answer 20

1. Absorbtion
2. Spontaneous emission
3. Stimulated Emission:

Question 21

Three important processes of lasers

Answer 21

1. Absorbtion
2. Spontaneous emission
3. Stimulated Emission:

Question 22

absorbtion

Answer 22

electron absorbs a photon and “jumps up” to an excited state.

Question 23

Spontaneous emission

Answer 23

Electron spontaneously de-excites, and releases a photon

Question 24

Spontaneous emission

Answer 24

Electron spontaneously de-excites, and releases a photon

Question 25

Stimulated Emission:

Answer 25

Electron de-excites as a result of a stimulus. The stimulus is an external photon. This is weird! It is a similar process to “absorbtion”, but the electron de-excites

Question 26

Stimulated Emission:

Answer 26

Electron de-excites as a result of a stimulus. The stimulus is an external photon. This is weird! It is a similar process to “absorbtion”, but the electron de-excites

Question 27

types of atomic transitions

Answer 27

Question 28

Lifetime of electrons

Answer 28

When one (or more) electron(s) are not in their lowest possible energy state, we say that an atom is in an excited state. We don’t know when a particular electron will de-excite. In other words, the lifetime of the excited state of a particular atom cannot be predicted

Question 29

equation to find out how many atoms are in excited state

Answer 29

If 𝑁_0 is the number of atoms in an excited state at 𝑡=0, then at some time, 𝑡, later we have 𝑁(𝑡)=𝑁_0 𝑒^((−𝜆𝑡) ) atoms in an excited state. Different atoms (e.g. 𝐻, 𝐻𝑒, 𝐿𝑖) have different lifetimes; i.e. different decay constants 𝜆

Question 30

Half life

Answer 30

The time it takes for half of a large collection of atoms to de-excite to their ground state

Question 31

Derviving half life equation

Answer 31