Class period
Chapter 4: The Atom
CHEM 6 know and understand the historical development of atomic theory.
You can
Describe the history of the atom and contributions of scientists: J. J. Thomson, John Dalton, Ernest Rutherford
name and identify the subatomic particles of the nucleus of an atom.
describe the properties of the subatomic particles of the nucleus of the atom.
name and identify and subatomic particle that surrounds the nucleus of the atom.
describe the properties of the subatomic particle that surrounds the nucleus of the atom.
define atomic number and identify what element it represents using the periodic table
identify the element symbol with a given atomic number.
define isotope and draw a nucleus of an atom’s particular isotope.
identify the differences and similarities between isotopes of the same atom.
define mass number and correctly write the symbol and name of an atom’s particular isotope.
Ch 4 Related assignments:
Back to Basics Atom quiz
p 91 #2, 5;
p97 #7, 8, 9
Ch 4 test
Rutherford’s experiment
p 99 #11-13; p101 #14;
p104 #18 - 21
Back to Basics Atom quiz
Main ideas:
 Atomic structure – protons, neutrons, electrons
 # protons identifies an atom
 Isotope – atom with a different number of neutrons
 Ion – atom that has lost or gained an electron(s)
 Nuclear reactions involve the nucleus and thus change the ID of an atom
Indirect measurement of electrons, aka Rutherford’s experiment
Follow up questions:
1. What does it mean to measure something indirectly?
2. What does this have to do with atoms?
Atomic theories – the old stuff – use online or your textbook to fill in A – G. Due __
A: Democritus’s Ideas
- dates lived:
Matter is ___________________________________
Atoms are ________________________________________
Different properties of matter are due to ______________________________
Changes in matter depend on _________________________________
B: Aristotle’s Ideas
- dates lived:
Did not believe in ______________________________________
Did not like __________________________ideas and renounced them
More popular thinker so Democritus’s ideas were knocked out for ________ years!
C: John Dalton
- dates lived:
Matter is made of _________________________________
All atoms of an element are _____________________________________
Atoms cannot be _________________________________
In a chemical reaction, atoms are __________________________________
D: J.J. Thompson
- date of discovery:
Accidentally discovered ___________________
What is a Cathode Ray Tube? ______________________________________
Draw a picture of a Cathode Ray Tube
E: Plum pudding theory, aka the chocolate chip cookie theory – electrons disbursed evenly
throughout an atom like chocolate chips in batter. Draw a model for this theory and label the
F: Rutherford
- date of discovery
What did Rutherford do?
Discovered evidence of __________________________
Label the drawing with
Radioactive source
Alpha particle stream
Gold foil
Detecting screen
What is the charge of an alpha, α, particle?
If the gold atoms had evenly distributed electrons, like the Plum Pudding model
suggested, all the positive charge would have gone straight through. They didn’t. They
bounced in all different directions.
Why? (Remember: different attracts, like repels)
G: Nuclear Model
Label each diagram below as either a Plum Pudding Model or a Nuclear Model
+ charge alpha
+ charge alpha
+ charge alpha
+ charge alpha
Stop filling in notes on your own here
Atom parts
Really, really, really _____
World population is _____________________ people
One penny has ______________________________________copper atoms in it
Atom size demo
The Atom’s Family
Nucleus –
 Located _________________________________
 Always has a ____________________ charge
 Made of protons
o Mass of _____
o Charge of ________
 And neutrons
o Mass of __________
o Charge of __________
o Joke: a neutron walks into a bar and orders a drink. He asks the bartender how
much. The bartender answers “For you? ______________________”
# of protons does _____ have to equal # of neutrons.
VERY _________. If nucleus was the size of a period on this page, it would weigh = to
_______% of atom’s _______
Surrounded by the __________________________
Atom is mostly ______________________. Size of the atom is _______________ the
size of the nucleus. About the same as a ___________ compared to the size of a
 Moves 2/3 the speed of light around the nucleus
 Mass of _________________
 Charge of _________________
 In a NEUTRAL atom, number of electrons always _______________________________
 Addition or subtraction of electrons is a ___________________________________
Summarize atomic structure in three sentences
HW p91 #2, 5
p97 #7, 8, 9
Characteristic of atoms
All atoms of one type of element share some characteristics. On periodic chart, looks like…
# of protons = # electrons in neutral atom
Mass of nucleus: protons + neutrons
Chemical name - self explanatory
Atomic number = _________________________
Symbol – 1, 2, or 3 letters, first always __________________. Why?
Mass – average mass of NEURTONS + PROTONS
Measured in amu – atomic mass unit
Not exactly the same as the number of neutrons + number of protons because of isotopes
(see next page). For our ID purposes, round off to the nearest ______________________.
Number of neutrons = mass minus atomic number (big # - little #)
i.e. Number of neutrons =
Remember, normal single atoms are electrically __________ b/c ___________________.
Atom changes
An atom that has __________________________________
Can be _______________ or _______________
DOES have a __________________________
Joke: two ions are walking down the road. One says “I think I lost an electron”. The other
says “Are you sure?” The first one answers “Yea, I’m __________________”
 Atoms with same number of protons and electrons but different numbers of
o Charge of atom _______________
o Identity of atom _______________
o Chemical behavior ________________
o Mass of atom _____________
 naturally occurring
 ways to write isotopes
o name and mass
 example: gold – 198
hydrogen – 2
 what does the number represent?
o mass/number and symbol
 example: 198
 what does the top number represent?
 What does the bottom number represent?
Atomic #
HW p99 #11-13
p101 #14
Atomic mass Mass/number
p104 #18 - 21
Chapter 25: Nuclear Reactions
CHEM 12 understand the basic processes of nuclear chemistry.
You can
 Demonstrate the use of symbols, formulas, and equations in describing nuclear reactions.
 Explain and balance nuclear equations.
 Compare fission and fusion reactions in terms of the masses of the reactants and products and the
amount of energy released in the nuclear reactions.
Ch 25 Related assignments:
HW p106 #23 – 27
Ch 4 test
Nuclear ws
Nuclear testing video -
Bikini Island -
Nuclear reactions
 A change in the ____________________
 A chemical change involves electrons only and does not alter the nucleus
 Atom nuclei decay (break apart) or combine to __________________________________
o Remember, protons determine the identity of an atom.
 Involves ENORMOUS amounts of energy
 Fusion
o Two of more nuclei ____________________________
o Produces one NEW element
o The result of an extremely high energy collision
o Occurs in _________
o We have not mastered this process yet.
 Fission
o A nuclei _____________________________
o Produces two or more NEW elements
o The result of an unstable ratio of neutrons to protons in the nucleus
o Happens spontaneously
o Used in ______________________ and ______________________
Radiation – the energy or particles released in a nuclear reaction
Radioactivity – the process of releasing radiation
If two atoms are put together to make one, what is the process called?
How do you know the identity of an atom?
What are three ways to tell if a reaction is chemical or nuclear?
Nuclear ws
Alpha radiation decay
 Occurs spontaneously in atoms with an atomic number greater than ______
 Alpha particles – two protons and two neutrons are physically ejected from the atom
o Which atom has 2 protons and 2 neutrons?
 Charge  Symbol –
 Used by ______________________
 Blocked by paper
Nuclear equation for alpha radiation – 21084 Polonium  20682Lead + 42He
Negative Beta radiation
 Happens when there are ______________________________________
 Beta particles – an electron is physically ejected from the nucleus
o Hey, wait a minute, there aren’t electrons in the nucleus
o Neutron splits into a positive proton that stays in the nucleus and a negative
electron that is shot out
 Charge –
 Symbol –
 Blocked by metal foil
 Nuclear equation for negative beta radiation – 146Carbon  147nitrogen + 0-1β
o Notice: atomic number goes _____ while atomic mass is _______________.
Remember, atomic number is how many protons. Atomic mass is the total of
protons and neutrons. One neutron becomes one proton.
Positron emission/Positive Beta radiation
Happens when there are too many _____________________
Proton sheds its positive aspect and becomes neutral – a neutron
The ‘positive aspect’ is called a positron and it radiates from the nucleus.
Happens when there are ______________________________________
Blocked by metal foil
Gamma radiation
rays of very high energy
No actual particles radiating from the atom.
No change in atom’s composition or identity.
Millions are going through you right now!
Not blocked by lead or concrete
How’d they figure all this out?
The diagram shows the paths of alpha, negative Beta, positive Beta, and Gamma radiation.
Positive plate
Negative plate
What are the charges for each type of radiation?
A woman’s turn – one of the most influential people in the history of nuclear research is Marie
Currie. Marie and her husband Pierre began studying nuclear
chemistry in the late 1880’s. Together they won a Nobel Prize in
physics. After her husband died in 1906 she went on to win a
second Nobel Prize, this time in chemistry. She is the only person
to ever win a Nobel Prize in both physics and chemistry. Because
radiation was only being discovered during her research, there was
a lack of understanding that protection from radiation exposure was
needed. Madame Currie died from radiation poisoning in 1934. Her
accomplishments include developing a theory of radioactivity (she
coined the term, too), isolating isotopes, discovering Polonium and
Radium and beginning the research into cancer treatments.
If a radiation product is made of two neutrons and two protons, what kind of radiation was it?
What do the numbers in front of the radiation symbols, such as α, mean?
What are three ways to tell if a reaction is negative Beta?
HW p106 #23 - 27