1. The Nature of Matter and Radioactivity
Physics 30 Unit 4 Review
The Nature of Matter
and Radioactivity

2. The Nature of Matter Atomic Theories: indivisible
The Greeks: The atom is the smallest, ____________ part of an element that can still be called an element.

3. Thomson:
negative
Discovered that the electron has a _____________ charge and also found the ____________________ ratio of the electron.
charge to mass
cathode ray
He performed his experiments with ____________________ tubes.
raisin bun
His model of the atom is called the _________________ model.
Formulas:
Fm = Fc
Remember:
CRT v2
x x x
qvB = r
mv2
F = ma
ac= r m Br q = v
mv2 r
Fc=

4. Mass Spectrometer:
Velocity Selector
Perpendicular Electric and Magnetic fields
Ion Separator
Just a magnetic or electric field + X X X X X X
Charged
particles X X X X X X X X X _
If accelerated by a potential difference then the formulas are:
If the particles travel through undeflected, then the formulas are:
Formulas are:
𝐹 𝑚 = 𝐹 𝑐
𝐸=𝐸
𝐹 𝑚 = 𝐹 𝑒
𝑞𝑣𝐵= 𝑚 𝑣 2 𝑟
𝑉𝑞= 1 2 𝑚 𝑣 2
𝑞𝑣𝐵= 𝐸 𝑞

5. Properties of Cathode Rays:
Cathode rays have the same properties no matter which type of ____________ is used for the cathode.
metal
straight
Cathode rays travel in ______________ lines.
electric E
Cathode rays can be bent in both _________________ and ___________________ fields.
magnetic B
Cathode rays can cause chemical reactions similar to _______________ (develop photographic film).
light
Cathode rays leave a vapour trail when they pass through a _________________ as well as a ___________________.
gas chamber
bubble chamber
electrons
Cathode rays are ________________.

6. Thomson Example:
A negatively charged particle is travelling with a speed of 1.43x106 m/s through a magnetic field of 2.50x10-3 T. The particle follows a curved path of radius 3.25x10-3 m. What is the charge to mass ratio of this particle?
Fm = Fc
qvB = r
mv2 m Br q = v =
1.43x106 m/s
(2.5x10-3 T)
(3.25x10-3 m)
= 1.76x1011 C/kg

7. Millikan’s Oil Drop Experiment:
negatively
He balanced ______________ charged oil drops between electric plates. When the particles were suspended, the ____________ force equaled the _____________ force.
electric
gravitational
+ plate Fe
- Oil drop Fg
- plate

8. Millikan’s Oil Drop Experiment (Formulas):
If the oil drop is suspended:
If the oil drop accelerates up:
Fe = Fg
Fe = Fg + Fa
E q = mg
E q = mg + ma
If the oil drop moves with a constant speed up or down:
If the oil drop accelerates down:
Fe = Fg - Fa
Fe = Fg
E q = mg - ma
E q = mg

9. Millikan’s Oil Drop Experiment (Graphing):
Oil drops of different weights are suspended between electric plates requiring different electric field strengths

10. Millikan’s Oil Drop Experiment (Graphing):
Line of best fit should:
Average the data points the best
Go through as many points as possible
Weight of Oil Drops
(x10?? N)
You can leave some points above
and below the line.
Slope Calculation:
Try not to choose data points
Electric Field Strength
(x10?? N/C)
Choose points as far apart
as possible
Fe = Fg mg
= q = e-
E q = mg E

11. Rutherford’s Scattering Experiment:

12. Rutherford’s Planetary Model:
scattering
Rutherford performed a ______________ experiment.
alpha
____________ particles were aimed at a layer of thin gold.
photographic
The particles were detected by ______________ film.
He concluded that the nucleus is:
tiny
Very ____________
positive
protons
Contains ________________ charges called __________.
electrons
__________ orbit the nucleus like planets orbit the sun.

13. Rutherford’s Planetary Model (Formulas):
electric
There is an _______________ force between the __________electrons and __________protons. This is because ______________ charges attract.
negative
positive
opposite
Since this force acts inwardly as the electron travels around the nucleus, it is also equal to the ____________ force.
centripetal
Example: Calculate the speed of the electron as it orbits the nucleus of a hydrogen atom if it’s orbital radius is 5.29x10-7m.
Fe = Fc = r
mv2 r2
kqq
(8.99× 10 9 )(1.6× 10 −19 )(1.6× 10 −19 ) 5.29× 10 −7 (9.11× 10 −31 )
v =
= 2.19x104m/s

14. Maxwell’s Problem:
According to Maxwell, any accelerating charge produces _____________ which travels at the speed of ___________.
light (c)
EMR
This can be shown with symbols:
∆ Ε Δ 𝐵 ∆ Ε
Since the electron in an atom is traveling in a circular path (it’s _____________ is always changing) it can be considered to be accelerating even though it’s speed is constant.
direction
The electrons within atoms are accelerating charged particles. They should give off _____________ (a form of energy) as they travel. They should thus lose energy and collapse into the atom.
EMR

15. Bohr Model of the Atom:
Within certain orbitals (a certain distance from the nucleus), electrons are free to travel without giving off any ___________.
EMR
energy
These orbitals are also called ___________ levels. The lowest energy level (closest to the nucleus) is called a ______________ state. The energy required to free the electron from the atom is called the _______________ energy.
ground
ionization
EMR
When electrons drop energy levels, they give off ___________.
When electrons move up energy levels, they have either been hit by an ___________ or an ______________.
electron
EMR photon

16. Formulas used with the Bohr Model:
𝐸𝑀𝑅 𝑔𝑖𝑣𝑒𝑛 𝑜𝑓𝑓
ℎ𝑖𝑡 𝑏𝑦 𝑎𝑛 𝑒 −
or photon
positive
negative
Energy levels can be written as ____________ or ____________ numbers.
subtract
_____________ the energy levels to find the energy difference between orbitals.
EMR Formulas
e- Formulas
𝜀= 1 2 m 𝑣 2
𝜀= ℎ𝑐 𝜆
𝜀=𝑉𝑞
𝜀=ℎ𝑓

17. Hydrogen Atom:
If the electron drops to the first (lowest) orbital, then _______________ is most likely released.
ultraviolet
If the electron drops to the second orbital, then _______________ is most likely released.
visible light
If the electron drops to the third orbital, then _______________ is most likely released.
infrared

18. Continuous Spectra:
Light from a hot glowing solid (like an incandescent light bulb) will produce a continuous spectrum in the visible region.
Prism
Diffraction Grating 𝑟 o y g b i v 𝑟 v
White light
White light 𝑣 r
Smaller wavelengths (blue) light is refracted more.
Longer wavelengths (red) light is diffracted more.
Blue bends more.
Think of the sky – it’s blue because the red light light is diffracted more.

19. Emmission Spectra:
electrons
Light from an excited elemental gas (excited by ___________ passing through it) will emit certain wavelengths of light. If this light is passed through a diffraction grating, a ______________ line pattern will be produced. Each element has a _____________ pattern.
bright
unique
Absorption Spectra:
When light passes through a cool elemental gas, certain ______________ of light are absorbed. These will appear as _________ lines on a spectrum.
wavelengths
dark

20. Example:
What is the wavelength of EMR released when an electron within an atom drops from an energy level of 12.0 eV to 8.5 eV?
E= 12.0 eV – 8.5 eV = 3.5 eV
𝐸= ℎ𝑐 𝜆
𝜆= ℎ𝑐 𝐸
𝜆= (4.14× 10 −15 )(3.00× 10 8 ) 3.5𝑒𝑉
𝜆=3.55× 10 −7 m

21. Compton Effect:
He performed a scattering experiment where EMR (___________) were fired at electrons. He found that the electrons moved off with speed after the collision and that the scattered x-rays had a ______________ wavelength.
photons
longer
He concluded that EMR can have a mass property: ___________________.
momentum
Momentum formula for masses:
𝑝=𝑚𝑣
𝑝= ℎ 𝜆
Momentum formula for EMR:
𝐸=𝑝𝑐
Δ𝜆= ℎ 𝑚𝑐 (1−𝑐𝑜𝑠𝜃)
The biggest angle an x-ray can be scattered is straight back _________
180o

22. Example:
An X-Ray of wavelength nm scatters at an angle of Calculate the wavelength of the scattered photon.
30o
Δ𝜆= ℎ 𝑚𝑐 (1−𝑐𝑜𝑠𝜃)
Δ𝜆= 6.63× 10 −34 (9.11× 10 −31 )(3.00× 10 8 ) (1−𝑐𝑜𝑠30)
Δ𝜆=3.25× 10 −13 m
𝜆 𝑓 = 𝜆 𝑖 +Δ𝜆=0.0500× 10 − × 10 −13 = 5.03× 10 −11 𝑚

23. de Broglie Wavelength:
Proposed that masses can have an EMR property: ___________.
wavelength
Objects with mass and speed travel with a ______________. The effect is only detectable for very small masses traveling at high speed. The formula below should be given to you on a diploma exam.
wavelength
𝑝 𝑚𝑎𝑠𝑠𝑒𝑠 = 𝑝 𝐸𝑀𝑅
𝑚𝑣= ℎ 𝜆
6.63× 10 −34
𝜆= ℎ 𝑚𝑣
𝑚𝑎𝑠𝑠 𝑎𝑛𝑑 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒

24. Example:
Calculate the wavelength of an electron that has been accelerated through a potential difference of V using the de Broglie wavelength formula
𝜆= ℎ 𝑚𝑣
𝜆= 6.63× 10 − × 10 −31 (??)
𝜀= 𝜀
1 2 𝑚 𝑣 2 =𝑉𝑞
𝜆=2.75× 10 −11 𝑚
𝑣= 2𝑉𝑞 𝑚
𝑣= 2(2000𝑉)(1.6× 10 −19 ) 9.11× 10 −31
𝑣=2.65× 10 7

25. Electron Orbitals:
Electrons really travel in a ____________ pattern as they travel around the nucleus of the atom.
wave
There must be a whole number multiple of wavelengths as the electron orbits the ___________.
nucleus
𝑛𝜆=2𝜋𝑟
You do not have to memorize this formula for the diploma.

26. The Standard Model of the Atom:
Particles responsible for Forces are called ______________ particles.
boson
Boson
______________ particles responsible for the following Forces (listed from strongest to weakest):
The strong nuclear force: __________________
gluons
The electromagnetic force: __________________
photons
The weak nuclear force: __________________
W+ W- Zo
graviton
The gravitational force: __________________ (undetected)

27. The Standard Model of the Atom:
Particles that make up matter are called ______________.
fermions
Very small particles that are elementary particles are called ___________________. The electron and it’s neutrino are _________________.
leptons
leptons
Larger particles, like neutrons and protons are called ___________________. They are made up of ___________________.
hadrons
quarks
_____________ are made up of 2 quarks.
Mesons
_____________ are made up of 3 quarks.
baryons

28. n p p n The Standard Model of the Atom: uud
Protons are made up of the following quarks: _____________ n 1 p 1 + 𝛽 -1 + 𝜐
udd
neutrons are made up of the following quarks: _____________ p 1 n 1 + 𝛽 1 + 𝜐

29. Radioactivity:
half
Particles that undergo radioactive decay, lose __________ their mass over a certain period of time. This time is called _________________.
half life
During this process, a radioactive element changes into another element, giving off particles or EMR. This is called __________________.
transmutation
Formulas:

30. Graphing Radioactivity:Bq
Radioactivity has lots of different units: __________, ___________, ____________, ______________ to list a few.
Bq/s
rads
decays / s

31. Terms:
neutron or a proton
Nucleon: __________________________
number of protons (bottom number)
Atomic Number: _______________
The atomic number identifies the element.
number of protons and neutrons (top number)
Mass Number: _______________
Conservation of Nucleons: _____________________________
___________________________________________________
the sum of the top numbers on both
sides of an equation must be equal.
Conservation of Charge: _____________________________
___________________________________________________
the sum of the bottom numbers on
both sides of an equation must be equal.

32. c N 3 Types of Radioactivity:
1. Beta Decay: assume beta negative for just “beta decay”
Beta Negative Decay: is an _________________.
electron 𝛽 -1 𝑒 -1
symbols are: __________________
an antin-eutrino is also released _________. 𝜐
Example: Write the decay equation for carbon 14 emitting a beta negative particle. c 14 6 N 14 7 + 𝛽 -1 + 𝜐

33. c B 3 Types of Radioactivity:
Beta Positive Decay: is an _____________________________.
antimater electron (positron)
1 0 𝛽
symbols are: __________________
a neutrino is also released __________. 𝜐
Example: Write the decay equation for carbon 14 emitting a beta positive particle. c 14 6 B 14 5 + 𝛽 1 + 𝜐

34. 3 Types of Radioactivity:
2. Alpha decay: is the nucleus of a ____________ atom.
helium
Symbols are: ___________________
2 4 𝛼 2+
2 4 𝐻𝑒 2+
Example: Write the decay equation for nitrogen 15 emitting an alpha particle.
7 15 𝑁
2 4 𝛼 2+ 𝐵

35. 3 Types of Radioactivity:
3. Gamma decay: is a high energy, high ____________, small ______________ EMR photon.
frequency
wavelength
Symbol is: __________________ 𝛾
0 0 𝛾
Example: Write the decay equation for cobalt 56 emitting a gamma ray.
27 56 𝐶𝑜
𝛾 +
27 56 𝐶𝑜

36. Penetrating Ability:
In order of increasing ability to penetrate objects:
thick paper or cardboard
Alpha particles: ___________________
Beta particles: ___________________
thin metal
lead (dense metal)
Gamma Rays: __________________________

37. Ability to Ionize (danger / risk):
In order of increasing risk:
higher energy due to increased speed
Beta particles: __________________________
higher energy due to larger mass
Alpha particles: __________________________
higher energy due to larger frequency
Gamma Rays: __________________________
or smaller wavelength

38. Li Binding Energy: neutrons
Is the energy exerted by the ___________ of an atom to hold the ______________ charged protons tightly in the nucleus.
positively
Some mass of the ___________ is converted into energy.
neutrons
Formula:
Example: The mass of a lithium-7 nucleus is u. What’s the binding energy? Li 7 3
3 𝑝 + =3(1.6726× 10 −27 𝑘𝑔)
4𝑛 =4(1.6749× 10 −27 𝑘𝑔)
× 10 −26 𝑘𝑔
𝑢 (1.66× 10 −27 𝑘𝑔/𝑢) = × 10 −26 𝑘𝑔
× 10 −26 − × 10 −26 = × 10 −29
𝐸=𝑚 𝑐 2 = × 10 − × =6.38× 10 −12 𝐽

39. Is the ____________ of an atom into other elements.
Nuclear Fission:
splitting
Is the ____________ of an atom into other elements.
Is the process used in ________________ power plants.
nuclear
Formula:
Example: Calculate the energy produced in the following fission reaction.
235 U + 1
140 94 1 n Xe + Sr + 2 n
Mass of reactants
× 10 −25
Mass of products
× 10 −25
235
U=3.9029x10-25 kg
Mass difference
3.251× 10 −28 1 n
=1.6749x10-27 kg
Binding Energy E=mc2
140 Xe
=2.3234x10-25 kg
3.251× 10 −28 ( 3.00× 10 8 ) 2 94 Sr
=1.5595x10-25 kg
2.9259× 10 −11 𝐽

40. Is the ____________ of simpler atoms into heavier elements. fusing
Nuclear Fusion:
Is the ____________ of simpler atoms into heavier elements.
fusing
sun
Is the process going on inside the ________________.
Formula:
Example: Calculate the energy produced in the following fusion reaction. 2 + 3 4 1 H H He + n
Mass of reactants
8.4526× 10 −27 1 1 2
Mass of products
8.3212× 10 −27 2
H=3.4444x10-27 kg 1
Mass difference
1.314× 10 −28 1 n
=1.6749x10-27 kg
Binding Energy E=mc2 4 He
=6.6463x10-27 kg
1.314× 10 −28 ( 3.00× 10 8 ) 2 3 H
=5.0082x10-27 kg
1.1826× 10 −11 𝐽 1