Atomic Structure
Unit 4: Ch 18.1-2, 7.1, 9.1-2, 4
Geo Ch ??
Reading the Periodic Table
Practice - Label this own on
your own!
What are different ways
of identifying atoms?
• Atomic Number: Equal to the number of
protons (+)
• Examples:
•H=1
•C=6
•O=8
What are different ways
of identifying atoms?
• Mass Number:
• Unit of measurement = amu (atomic mass unit)
• 1 proton = 1 amu
• 1 neutron = 1 amu
• 1 electron = 0 amu (too light to count)
• Reminder: Round to the closest whole number
What are different ways
of identifying atoms?
MASS NUMBER = PROTONS + NEUTRONS
or
NEUTRONS = MASS NUMBER – ATOMIC NUMBER
Example: How many neutrons are in U-236?
Neutrons = 236 – 92 = 144 neutrons
Determining Charge
Electron =
negative
+
-3
+3
=0
Proton =
positive
Practice – Determine
charge on your own!
Ions
• The previous example had a charge
• An atom that has a charge is called an ion
• A positive ion = cation
• A negative ion = anion
Ion Symbols
Atomic number (protons) = 3
Charge = +3 + -2 = +1
Element symbol = Li
Ion symbol = Li+
Practice – Write ion
symbol on your own!
Making Ions
• Changing number of neutrons =
changing mass number
• Changing number of protons =
changing atomic number = different
element
• Changing number of electrons =
making atom charge = ION!
Isotopes
• Atoms of the same element do not always have the same
number of neutrons
• These are called isotopes
• The atomic number (number of protons) DOES NOT change
• The mass number (protons plus neutrons) DOES change
Mass number
Atomic number
Isotope Symbols
Isotope Symbols
1. What is the element
symbol?
2. What is the name of the
element (find on
periodic table)?
3. What is the atomic
number?
4. What is the mass
number?
5. How many protons does
this element have?
6. How many neutrons
does this element have?
Practice- Answer these
questions on your own!
1. What is the element
symbol?
2. What is the name of the
element (find on periodic
table)?
3. What is the atomic
number?
4. What is the mass number?
5. How many protons does
this element have?
6. How many neutrons does
this element have?
Warm-Up
Fill in the missing information:
Element
Boron
Atomic
Symbol
B
Number
of
Protons
Number Number Mass
of
of
Number
Neutrons Electrons
Isotope
Symbol
5
Oxygen
Element
Atomic
Number
18
Atomic
Symbol
Number of
Protons
Number of
Electrons
Atomic
Number
Ion
Symbol
N-3
Electric Charge, pg. 194-201
•
•
•
•
•
•
•
•
•
•
Can be positive (protons)
Can be negative (electrons)
When they are even, the atom is neutral.
Some atoms hold their electrons more tightly than others.
To become positively charged, atoms must ____
electrons.
To become negatively charged, atoms must ____
electrons.
Law of Conservation of Charge
Charge, force, distance relationship?
Conductors vs Insulators
Charge by contact vs Charge by induction
Check for Understanding
1. How do you make an object positively charged?
2. How do you make an object negatively charged?
3. What are two ways to charge an object? (Hint: charging
by ___ or ___.)
4. What happens to two positive charges brought near
each other (attract/repel)?
5. What happens when a positive and negative are brought
near each other (attract/repel)?
6. If two charges are brought closer together, what
happens to the force?
7. If one charge is increased, what happens to the force?
8. State the law of conservation of charge.
Warm-Up
1. What do these picture make you think of? Write
down as many things as you can!
Nuclear Fission
• Fission and Fusion Video
• Fission means “to divide”
• The process of splitting a nucleus into two nuclei
with smaller masses
• This occurs when a neutron hits the nucleus of an atom
• Only large nuclei can underdo fission reactions
• The total mass of the products is slightly less than the
mass of the original nuclear and the neutrons that
break free
• The missing mass is converted into large amounts of
energy
Nuclear Fission
Lighter
element
Neutrons
Neutron
+ Energy
Uranium - 235
Lighter
element
Nuclear Fission
• The free neutrons released from the original
nucleus hit other atoms and cause a chain
reaction
energy
energy
energy
energy
energy
energy
Nuclear Fusion
• The process of combining two low mass nuclei
into one larger mass nucleus
• On the Sun, this process occurs using hydrogen
nuclei
• Overall, 4 hydrogen atoms fuse to form one helium
• Just like in fission, a small amount of mass is
converted into a large amount of energy
Nuclear Fusion
positron
energy
neutrino
positron
energy
neutrino
Energy to Mass Conversions
• Think back to the law of conservation of energy
• We need to include mass in this law when talking
about fission and fusions reactions
• This relationship is shown by Einstein’s theory of
relativity
• This states that energy and mass are equivalent and
can be converted using the equation E=mc2
Warm-Up
1. What type of nuclear reaction shown below?
2. Write an equation for the reaction. You only need to
include the symbol and mass number.
3. What type of nuclear reaction is shown below?
Radiation
• When a nucleus becomes unstable, it decays
releasing particles and energy called nuclear
radiation
• Radiation comes from radioactive isotopes, or
radioisotopes
• The release of radiation is called decay
• Some radiation is more powerful than others
• There are three types of nuclear radiation –
• alpha (α) – made of 2 p= and 2 n0
• beta (β) – n0 decays into p= and e- (beta particle)
• gamma (γ) – no mass or charge, just energy
Radiation, continued
• Alpha particles
• Large
• Cannot pierce deep into matter – easily stopped by thin layer
of material
• Beta Particles
• beta particle (small, light, fast)
• Can only be stopped by thick materials, like stacked sheets
of metal, blocks of wood or heaving clothing
• Gamma Radiation
• Travels in waves as electromagnetic radiation (or light)
• Can pass through most types of materials – need a material
thicker than blocks of concrete
Types of Radioactive Decay
Radiation, continued
Particle Type
Symbol
Mass
Charge
Alpha
Beta
4
2He
or α
4
+2
Gamma
β
0.0005
-1
γ
0
0
Radiation, continued
• Half-life
• The amount of time it takes for half of the nuclei
of a radioactive isotope to decay
• The original substance is called the parent
• The new substance is called the daughter
Warm-Up
1. What is the electron that is produced when a neutron
decays called? (choose from: alpha particle/beta
particle/gamma radiation)
2. What is a helium nucleus with two protons and two
neutrons called? (choose from: alpha particle/beta
particle/gamma radiation)
3. How many half-lives have passed when 1/16 of the
parent material remains?
4. What happens to the atomic number and mass number
when a beta particle is emitted?
5. What happens to the atomic number and mass number
when an alpha particle is emitted?
Warm-Up
1.
2.
3.
4.
What is fusion?
What is fission?
What is radiation/radioactivity?
Where does the energy produced in fission and
fusion reactions come from?