UNIT 1: Atoms, Patterns, and the Periodic Table
Part 1
Chemistry Fall 2015
Name ____________________________
Teacher _______________Hour _______
1
Unit 1: Atoms, Patterns, and the Periodic Table
KUDos are a way organizing our learning goals. By the end of this unit, you should:
KNOW: Things you need to ‘know’ are facts that you need to memorize and recall. They are like the ingredients in a recipe. You
cannot ‘understand’ or ‘do’ without these basics.




Chemistry
Property
Atom
Atomic Number




Proton
Neutron
Electron
Valence Electrons




Isotope
Mass Number
Average Atomic Mass
Atomic Sketch
UNDERSTAND: Things you need to ‘understand’ are big picture generalizations you need to generate. This is like the recipe. It is the
big picture/plan. This understanding helps you do the ‘do’.
A. Matter is classified by its physical and chemical properties.
B. Evidence gathered over hundreds of years has helped us to produce an ever more accurate model of the atom.
C. The physical and chemical properties of substances result from the types and arrangement of atoms in the substance.
DO: The things you need to ‘do’ are skills and processes that you need to independently do. These are like the different actions you do
to actually make a meal. You will be tracking your progress in the table below and you can check them off when you see you are ready
for the quiz.
1)
2)
3)
4)
5)
Define vocabulary words in the KNOW section.
Provide evidence for the structure of the atom. (protons, electrons, , neutrons, nucleus, mostly empty space)
Identify an element and its number of protons, electrons, neutrons, and mass number if you are given its atomic number
Create/draw a model of an atom that accurately shows the number & placement of protons, neutrons, and electrons
Draw an atomic sketch that represents the correct number of energy levels and number of electrons in each energy level.
CCRS SKILLS
E.24.5 Determine which model(s) is(are) supported or weakened by new information
2
KNOW: Chemistry, Property
Baggie Lab
An Introduction to Chemistry
PreLab Questions: Answer these question based on your experience. There are no right or wrong answers to these questions.
1. Based on your experience, what do you think chemistry is?
2. What do you think chemists do?
3. What things are important when designing an experiment?
Purpose: To investigate the unique properties of substances when they are alone vs combined with other substances.
Materials:
 1 dropper bottle of BTB (bromthymol blue)
 1 beaker of water
 calcium chloride (CaCl2)
 baking soda (sodium bicarbonate- NaHCO3)
 1-qt Ziploc bag
Procedure Part I
1. Record observations of each substance before the reactants are mixed.
Initial Observations
Calcium chloride
CaCl2
1.
2.
3.
4.
5.
6.
7.
8.
9.
Baking soda
NaHCO3
Water
H20
Bromthymol Blue
Solution (BTB)
Place a 1-quart Ziploc flat on the lab counter
Fill a spoon up to the BLACK line with baking soda and place into a corner of the Ziploc baggie.
Fill a spoon up to the BLUE line with calcium chloride and place into a second corner of the baggie.
Carefully inject 5 drops of bromthymol blue solution into a third corner of the baggie.
Carefully inject ONE pipet-full of water into the fourth corner of the baggie.
Quickly and gently close the baggie, keeping all four items separate.
Pick the baggie up off of the table. Holding the baggie upright, mix all four ingredients and record your observations.
Carefully wash out the baggie and dry the inside of it with a towel.
Repeat the experiment, leaving out 1, and only 1, ingredient each time. Record your observations for each trial in the
following table. Place a checkmark in each box if the substance was used, and a ----- if it was not used.
3
Data and Observations:
CaCl2
Part I
Trials
1
Baking soda
Water
BTB
Observations
2
3
4
5
10. For the Part II trials, leave out 2 ingredients for each trial.
Part II
Trials
1
CaCl2
Baking soda
Water
BTB
Observations
2
3
4
Questions:
1. Based on your observations, Can you tell
a. Which ingredient is responsible for the rise in temperature? Explain.
b. Which ingredient is responsible for the drop in temperature? Explain.
c. Which ingredient is responsible for the color changes? Explain.
d. Which ingredients are required to produce all the changes in Experiment #1?
Class definition of chemistry:
Class definition of property:
4
KNOW: Atom, Property
UNDERSTAND: The physical and chemical properties of substances result from the types and arrangement of atoms in the substance.
Why do we care about atoms?
We have seen that different substances have different properties, or characteristics. But why? We are going to make the connection
between the properties we can see with our own eyes, and the scale of atoms. An atom is the smallest unit of an element that
maintains the chemical properties of that element. In other words, it’s the smallest possible piece of an element, and cannot be broken
down. Sometimes people use the term “nanoscale” to describe the atomic level, since atoms are generally only a nanometer in length.
That’s one billionth of a meter, so pretty tiny! But can such tiny particles really make a difference?
We are going to use everyday objects to stand for atoms and the different ways they can be arranged.
1. Place two cups upside down, about 1 inch apart.
2. Peel off 2 Post-it notes and stack them as a flat bridge between the cups.
3. Place pennies one at a time on the middle of your Post-it note bridge. When the structure falls, count how many pennies you
used.
4. Roll up 2 Post-it notes. Use a pen or pencil to help roll the tubes, and use the sticky ends to seal the tubes closed.
5. Place the tubes across the gap between the cups.
6. Place pennies one at a time over your bridge. Like you did before, count how many pennies the bridge could hold.
Which bridge was stronger? Why do you think this is?
Imagine that your Post-it notes are made of millions of tiny carbon atoms (which, they sort of are, since paper is largely made of
carbon). The Post-its left as sheets are more like graphite, which is what we call pencil “lead.” In graphite, carbon atoms are arranged
in hexagons that join together in sheets, like in the picture on the left below:
Carbon Nanotube
Graphite
Because graphite is arranged in sheets, it’s easy for those sheets to slide past each other, and graphite is kind of brittle. On the other
hand, carbon can also be arranged in rolls of those hexagons, just like how you rolled up the Post-it. As you saw, this structure is much
stronger. We call carbon in this form carbon nanotubes, or CNT. It’s what makes really tough hockey sticks.
As you can see, it’s not only the type of atoms you have, but also how they are arranged at that tiny nanoscale that affects properties
like strength. We choose different materials for different purposes based on their properties.
So let’s back up and find out…what IS an atom in the first place? In the drawings above, small dots are used as a symbol for atoms,
but what do they really look like?
5
READING: Main Ideas of Five Models of the Atom
We are going to be learning about how models of the atom have changed through time, and practice a CCRS skill. But before we do
that, let’s get familiar with main ideas of the models we will be working with.
Use your Five Models of the Atom handout to complete the table below. The first row is completed for you as an example.
Model
Main Idea (MI.24.1)
Supporting Details (SD.20.1)
Solid sphere
The atom is a solid sphere.
Atoms cannot be broken into smaller pieces.
Plum pudding
Nuclear
Proton
Solar System
6
GOAL: E.24.5 Determine which model(s) is(are) supported or weakened by new information
GOAL 2: Provide evidence for the structure of the atom. (protons, electrons, neutrons, nucleus, mostly empty space)
Models of the Atom: How do we know what an atom looks like?
Use model descriptions on from your Models handout as we go along.
Background:
In 1803, John Dalton proposed that atoms were simply solid spheres. In the decades that followed, chemists collected a lot of evidence
suggesting that there was more to the atom. We will look at the five models of the atom, read their descriptions, and watch short videos
about how the pieces of evidence were collected. Then we will use the evidence to evaluate the models. It’s important to remember
that scientists are still adding to our knowledge of what an atom looks like, so the model can still change!
EVIDENCE 1: It is possible to remove a negatively charged particle from an atom using electrical forces. (Thomson, 1897)
1. Does the evidence better support the solid sphere model or the plum pudding model?
Let’s break it down:
a. Main characteristics of the solid sphere model (E.20.2):
b. Main characteristics of the plum pudding model (E.20.2):
c. Main idea of evidence 1 is that atoms must contain _______________________________.
d. Which model best matches evidence 1, based on your answer above? Explain.
EVIDENCE 2: If a tiny particle is shot into the middle of an atom, it hits something dense in the center and bounces back in
the direction from which it came. If a tiny particle is shot into the edges of the atom, it goes through. Most tiny particles shot
at an atom will go through. (Rutherford, 1911)
2. Does the evidence better support the nuclear model or the plum pudding model?
a. Main characteristics of the nuclear model (E.20.2):
b. Main characteristics of the plum pudding model (E.20.2):
c. Main ideas of evidence 2 are that the atom’s parts are most concentrated in its (center, edges) and that the edges of the atom must
contain mostly (particles, empty space).
d. Based on your answers above, which model is best supported by evidence 2? Explain.
7
3. EVIDENCE 3: Some electrons are easier to remove from an atom than others, suggesting that some electrons are farther
from the center of an atom than others. (Bohr, 1913)
This time, let’s identify whether evidence 3 supports or weakens each model:
a. Solid sphere model (supported/weakened). Explain your choice:
Example: Evidence 3 shows that there are smaller particles within the atom, but the solid sphere model has no
particles.
b. Plum pudding model (supported/weakened). Explain your choice:
c. Nuclear model (supported/weakened). Explain your choice:
d. Proton model (supported/weakened). Explain your choice:
e. Solar system model (supported/weakened). Explain your choice:
EVIDENCE 4. In 1932, British physicist James Chadwick discovered that the nucleus was made up of uncharged, or neutral,
particles called neutrons, in addition to the protons discovered by Rutherford. He also knew about Bohr’s experiments with
removing electrons from atoms.
Which model(s) is(are) supported or weakened by evidence 4?
a. Plum pudding model (supported/weakened). Explain your choice:
b. Proton model (supported/weakened). Explain your choice:
c. Solar system model (supported/weakened). Explain your choice:
d. Which model is the closest match with evidence 4? Why?
e. How could you revise the model so that it incorporates evidence 4? Draw a picture of an atom based on your model, and give
it a name.
8
Goal 2: Provide evidence for the structure of the atom. (nucleus, protons, electrons, neutrons, mostly empty space)
Fill in the table to describe the pieces of evidence which support the existence of each part of the atom.
Part of Atom
Pieces of Evidence that support it
Is it located in the
nucleus or outside the
nucleus?
What is its charge?
(positive, negative,
neutral)
Nucleus
Electron
Proton
Neutron
Mostly empty
space
Use the space below to draw important parts of the experiments that gave us the evidence.
Draw Rutherford’s gold foil experiment:
Draw Thomson’s cathode ray experiment:
How do we know the nucleus is made of both protons and neutrons?
9
Practice: Evidence for the Structure of the Atom
GOAL 2: Provide evidence for the structure of the atom. (protons, electrons, neutrons, nucleus, mostly empty space)
1. Rutherford’s gold foil experiment
a. Explain the experiment in words
b. List the conclusions of the Rutherford experiment
2. Cathode Ray experiment
a. Explain the experiment in words
b. List the conclusions of the cathode ray experiment
3. Rutherford’s gold foil experiment provided
evidence that the atom consisted of a
a. A small, positive nucleus
b. Mostly empty space
c. Electrons moved freely
d. A and B
e. A, B, and C
4. The cathode ray experiment provided
evidence that the atom consisted of :
a. A small, positive nucleus
b. Neutrons that were neutral
c. Electrons that were negative
d. Protons that were positive
e. All of the above
5. The conclusion that there was a positive nucleus 6. Neutrons were discovered based on an
from Rutherford’s experiment was because:
experiment with alpha particles, too.
a. The alpha particles were positive and
Neutrons are needed to make the nucleus
repelled the nucleus.
stable because:
b. The alpha particles were negative and
a. The negative protons would be
were attracted to the nucleus.
attracted to each other.
c. The alpha particles were positive and were
b. The positive protons would repel each
attracted to the nucleus.
other.
d. The alpha particles were neutral so they
c. The positive protons would be
didn’t have an effect on the nucleus.
attracted to each other.
10
GOAL: E.24.5 Determine which model(s) is(are) supported by new information
Directions: As you read the passage, summarize the supporting details of each model in the margin so it
will be easy for you to find the information you need later. One supporting detail is given for you.
Passage: Explaining the Extinction of the Dinosaurs
Asteroid-Impact (AI) Model
The dinosaurs disappeared at the end of the Mesozoic era, about
65 million years ago. The disappearance took place over a very short
period of time and was, according to some scientists, triggered by Earth
colliding with a large asteroid.
Today, evidence of this collision can be found in the rock record.
Geologists have discovered a thin layer of clay containing a high
concentration of the element iridium between 2 particular rock layers.
This boundary marks the end of the Mesozoic and the beginning of the
Cenozoic era. This iridium-rich layer has been identified at the
Mesozoic-Cenozoic boundary at many different locations around the
world. Iridium, while rare on Earth, is a common substance in
meteorites and asteroids.
The asteroid not only supplied the iridium, but its white-hot
rock fragments also started fires that engulfed entire continents. The
soot from these fires, combined with asteroid particles that were
propelled into the atmosphere, blocked out the Sun’s energy. The lack
of sunlight halted photosynthesis and caused a decrease in global
temperatures. Much of the plant and animal life, including the
dinosaurs, could not adapt to the temperature change and died.
Gradual-Extinction (GE) Model
Some scientists disagree with the asteroid-impact model. They
point to evidence that the dinosaurs died out gradually because of a
long-term climatic change.
Earth experienced increased volcanic activity 65 million years
ago. Not only could Earth’s volcanism have produced the iridium, but
more important, volcanoes did produce tremendous amounts of carbon
dioxide. The increased levels of carbon dioxide in the atmosphere
prevented Earth from radiating excess heat back into space, and thus
caused a worldwide warming.
The warming of Earth is what caused the dinosaurs’
disappearance. After examining dinosaur egg fossils, paleontologists
discovered that the eggshells became thinner in at least one species.
This was thought to be the result of heat adversely affecting the
dinosaurs’ metabolism. These thin-shelled eggs, which were easily
broken, lowered the survival rate among the offspring and contributed
to the eventual extinction of the dinosaurs.
Asteroid Impact Model
Main idea: extinction of dinosaurs was
caused by ______________________
Supporting detail: happened quickly
Gradual Extinction Model
Main idea: extinction of dinosaurs was
caused by ______________________
Supporting detail: happened gradually
11
Now choose the best answers to the questions, explaining your choices.
1. Astronomers recently estimated that only 3% of asteroids with orbits that
intersect Earth’s have been identified. Which model is supported by this
evidence?
A. The asteroid-impact model
B. The gradual extinction model
Explanation of choice
Example: The new information
suggests that asteroids are
common. That makes it more
likely that asteroids could have
affected the dinosaurs.
C. Both models are supported by the new information
D. Neither model is supported by the new information
2. A geologist examines a sedimentary rock layer from the MesozoicCenozoic boundary, finding evidence of great volcanic activity. Which model,
if any, would most likely be in agreement with this evidence?
Explanation of choice
A. The asteroid-impact model
B. The gradual extinction model
C. Both models
D. Neither model
3. Which piece of evidence do BOTH models suggest as a direct cause of the extinction of the dinosaurs?
A. High levels of soot and volcanic ash
Explanation of choice
B. High concentrations of iridium
C. Global temperature change
D. Increased amounts of carbon dioxide introduced into the
atmosphere
12
4. Some massive object periodically disrupts the solar system, causing
comets and asteroids to enter the inner solar system. Which model is
weakened by this information?
Explanation of choice
A. Asteroid-impact model
B. Gradual extinction model.
C. Both models are weakened by this information.
D. Neither model is weakened by this information.
5. The tilt of Earth’s axis changes every 26 million years, causing long-term climatic changes that lead to
mass-extinction episodes. Which model is weakened by this information?
A. Asteroid-impact model
Explanation of choice
B. Gradual extinction model.
C. Both models are weakened by this information.
D. Neither model is weakened by this information.
13
Skills Practice – E.24.5: Determine which models is/are supported or weakened by new information
Use the information below to answer the following questions.
Four hypotheses have been proposed to explain the origin of the Moon.
Sister Hypothesis
Earth and the Moon are about 4.6 billion years old. Because both formed from the same rotating cloud of gas and dust, their
average compositions are basically the same. Even the ratios of their oxygen isotopes (160, 170, 180 ) are the same. Both bodies
revolve around the Sun and rotate in the same direction.
Daughter Hypothesis
The early molten Earth once rotated much faster than it does today. The rapid rotation caused part of its iron-poor mantle to
tear away and move into orbit around Earth where it cooled to form the Moon. The average density of the Moon and the density of
Earth's upper mantle are approximately the same.
Capture Hypothesis
The Moon formed in another part of the solar system and was captured by Earth's gravity when the Moon passed close by.
The Moon originally orbited Earth in a direction opposite the direction of Earth's rotation. Earth's gravity acted to slow down the Moon
and its orbit decreased in size. Eventually the Moon's orbital path was reversed and it then moved in the same direction as Earth and
was gradually accelerated in its orbit by Earth's gravity. This explains why the Moon's orbit is increasing in size at a rate of about 3 cm
per year. Since the Moon formed in another part of the solar system, this may explain why Moon rocks have little water and iron, a lower
average density, and a higher abundance of uranium and rare-earth elements when compared to Earth rocks.
Giant Impact Hypothesis
A large Mars-sized body collided with the young Earth and caused a large cloud of debris (composed mostly of iron-poor
mantle material) to be flung into space. This cloud gradually accumulated to become the Moon. One reason the Moon lacks water and
other easily evaporated materials is that they were vaporized by the heat of impact. A computer model that simulates a collision of this
type very closely matched the Moon's size, rate of spin, and average composition. Moon rocks contain several isotopes that match
those in Earth's mantle.
1. _____Basalt, a rock indicating volcanic activity, is found on both the Moon and Earth. This information best supports which
theory?
a. Sister hypothesis
b. Daughter hypothesis
c. Capture hypothesis
d. Sister and Daughter hypotheses
e. Sister and Capture hypotheses
f. Daughter and Capture hypotheses
2. Explain your reasoning for your answer from above.
3. _____It has been found that specific oxygen isotopes have been identified in both Moon rocks and in rocks from Earth's
mantle. This new information provides the least amount of support for which hypothesis?
a. Sister hypothesis
b. Daughter hypothesis
c. Capture hypothesis
d. Giant Impact hypothesis
4. Explain your reasoning for your answer from above.
14
Use these pictures for the Super Atomic Microscope activity on the following page.
“SUPER” ATOMIC PICTURES!!!!
“SUPER” ATOMIC PICTURES!!!!
= neutron
= neutron
= proton
“SUPER” ATOMIC
PICTURES!!!!
= electron = proton
= electron
= neutron
3
1 +
1
PICTURES!!!!
H
H
H “SUPER” 2ATOMIC
H
3
1
2 proton
=
H
H
H
neutron
= =electron
= proton
3
1
2
H
H
H
= electron
1.0078 amu
Hydrogen
2.0140
1
H amu
1.0078 amu
2.0140 amu
Hydrogen
Hydrogen
Hydrogen
Hydrogen
12
C
1.0078 amu
12
13
6 p+
7 no
6p
6 no
25
12.0000 amu
Mg
24
CarbonMg
12.0000 amu
6p
6 no
Carbon
24
Mg
23.9850 amu
Magnesium
12 p+
12 no
24 12 p
24.9858
23.9850 amu
Mg
amu
12 no
+
6p
7 n26o
25
Mg
Carbon
12 p+
13 no
Mg
6p
7 no
+
12 p
25 25.9826
24.9858 amu
Mg
13 no
6 p+
o
137 n
C-
13.003 amu
+
Carbon ion6 po
7n
25
26
CarbonMgion
Carbon
Mg
-
C
Hydrogen
ion
13.003 amu
+
13.0034 amu
25
+
Carbon ion
13.0034 amu
+
H+
1.007813 amu
C-
6 p+
7 no
+
Carbon
+
1
1.0078 amu
13
12 6 pamu
136 p amu
13.0034
13.003
C
C
12.0000 amu 6 no
13.0034 amu
7 no
Carbon
H+
1.0078 amu
C
Hydrogen
+
1
Hydrogen ion
3.01606 amu
Carbon
C-
Hydrogen
2.0140 amu
6 p+
6 no
12.0000 amu
Carbon
13
3.01606
amu
13
C
C
Hydrogen
Hydrogen
3
1.0078
amu
H
3.01606 amu
H+
Hydrogen ion
Hydrogen
Hydrogen ion
C
Hydrogen
1.0078 amu
Mg
13
2.014012amu
C
Hydrogen
24
3.01606
amu
2
H
1
2+
Mg
6 p+
13.003 amu
Carbon
ion
26
Mg
amu
12 p+
14 no
+
26 12 p
24.9858
25.9826 amu
Mg
14 no
25
7 no
Mg2
25
Mg2+
amu
12 p+
13 no
25
Mg2+1
24.9858 amu 1
Magnesium
Magnesium
Magnesium ion
Magnesium 12 p+
Magnesium 12 p+
Magnesium 12 p+
Magnesium ion12 p+
o
o
o
23.9850 amu 12 n
24.9858 amu 13 n
25.9826 amu 14 n
24.9858 amu 13 no
Magnesium
23.9850 amu
Magnesium
12 p+
24.9858 amu
12 no Magnesium
Magnesium
12 p+
13 no
Magnesium
25.9826 amu
Magnesium
12 p+
24.9858ion
amu
14 no Magnesium
Magnesium ion
15
12
13
KNOW: proton, electron, neutron, mass number, isotope, atomic number
GOAL 3: Identify an element and its number of protons, electrons, neutrons, and mass number if you are given its atomic
number
The “Super” Atomic Microscope
Part I: The following activity is designed to help us look (hypothetically) inside an atom. We will take a look at what characterizes
atoms and what make each type of atoms special and unique. Throughout this activity you will need the Super Atomic Microscope
diagrams and a periodic table.
1. Look at the super atomic microscope pictures for hydrogen. What do all hydrogen atoms have in common (I.24.1)?
2. What do all carbon atoms and ions have in common (I.24.1)?
3. What do all magnesium atoms have in common (I.24.1)?
4. Look at your periodic table. What whole number is in the box for each of these elements (carbon, hydrogen, and
magnesium)? This number is called the atomic number. What do you think it represents?
5.
Look at your periodic table. How many protons are in all chlorine atoms? Do you think chlorine atoms exist with 16 protons?
Why or why not?
6. Here is a simple model of a Beryllium atom. Label the electrons, protons, and neutrons in the diagram, using your Periodic
Table to help you.
7. In the corner of each picture is the element symbol and the mass number for the atom. How is this mass number
determined? Why is it called a “mass” number?
16
8. Give the mass number for the following atoms:
9 protons
8 neutrons
5 protons
7 neutrons
8. Atoms of the same element that have different mass numbers are called isotopes. What makes all the isotopes of
magnesium the same? How do different isotopes of magnesium differ?
9. Considering what you now know about isotopes, do all atoms of an element have the same atomic mass? Explain why/why
not. Notice that the masses given on the Periodic Table are decimals.
10. Use your periodic table to give the name of the element on the left in question 7: _____________________
11. How many protons are in the element on the left from question 7? ____________ How many electrons? ______________
12. The total charge on each atom is zero. Explain why. (HINT: think of the charges that the particles have):
17
13. Complete the following table, using your periodic table.
Mass
Number
Mass
Number
Goal 4: Create/draw a model of an atom that accurately shows the number & placement of protons, neutrons, and
electrons.
Congratulations! You are becoming an atomic expert. Now that you’re getting good at finding numbers of protons, neutrons, and
electrons, let’s put all the information together to draw atoms.
Let’s summarize some of the important things we’ve learned so far:
a) Atomic number- tells the # of protons in the nucleus of an atom. The number of protons determines the element.
b) Mass number- the total n# of protons (p) added to the number of neutrons (n) in the nucleus. Tells the mass of an
atom (electrons are so small that practically do not contribute to the mass)
c) Number of electrons: Atoms have no charge most of the time, which means that they have the same number of
protons as the same number of electrons
By looking at a chemical symbol, you can determine the number of protons, neutrons and electrons.
o
o
o
Number of protons given by atomic number
Number of electrons equals number of protons (when the atom has no charge)
Number of neutrons: mass number minus the number of protons
40 – 19 = 21 neutrons
19 protons therefore, 19
electrons
40
19
K
18
Once you have figured out the numbers of particles, you’re ready to draw a model of atom that shows where the particles
are located. Let’s say we have an atom of 146C.
It has _________ protons that are located _______________. Use shaded dots to stand for protons in the space for your
drawing.
It has ________ neutrons that are located _______________. Use open circles to stand for neutrons in your drawing.
It has ________ electrons that are located _______________. Use triangles to stand for electrons in your drawing. We will
place our electrons in “orbits,” like in the solar system model. We will learn later that there are always 2 electrons in the first
orbit—don’t worry why for right now, but we will show it that way.
Drawing of 146C atom
Now it’s your turn to practice. If you get stuck, look at the example above or the Beryllium atom on p. 14 for help. For each drawing,
make sure you include the right number and location of protons, neutrons, and electrons.
1. Draw a model of an atom of 42He. Let’s break it down first:
Number of protons ____________ number of neutrons _____________ number of electrons _____________
Now put the particles in the right places in a drawing:
2. Draw a model of an atom of 73Li:
3.Draw a model of an atom of 115B:
4. Draw a model of an atom of 168O:
Remember how we learned that the solar system model of the atom shows electrons at different distances from the nucleus? Our next
lab will provide us with evidence similar to what Bohr saw, and we will see how the electrons affect the properties of atoms.
19
Practice: Identifying elements and drawing atomic models
Goal 3: Identify an element and its number of protons, electrons, neutrons, and mass number if you are given its atomic
number
1. This element is Fluorine. Use this information to complete the following tasks.
a. What is Fluorine’s atomic number?
b. What does the atomic number (of ANY atom) represent?
c. How many protons does Fluorine have?
d. How many electrons does Fluorine have?
e. What is the average atomic mass of F?
2. What is the charge of a:
a. Proton =
b. Neutron =
c. Electron =
3. For the following elements, list the number of protons, and electrons in each. Use your periodic table.
a. Sodium:
c. Copper:
b. Silicon:
d. Bromine:
4. This is the chemical symbol for Chlorine:
35
Cl
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a. Place a circle around the number that represents the mass number.
b. Place a square around the number that represents the atomic number.
c. How many protons, neutrons and electrons are found in this atom of Chlorine?
5. Define the term isotope. (If you can’t remember, look back at the previous pages to find this term).
6. Are these two atoms isotopes of one another? How do you know?
14
7
7. Are these two atoms isotopes of one another? How do you know?
16
8
N and
O and
15
7
32
16
N
S
Goal 4: Create/draw a model of an atom that accurately shows the number & placement of protons, neutrons, and electrons
8. Draw a model of an atom for each of the following elements:
a. Oxygen (mass
b. Boron (mass
number =16)
number =11)
GOAL: E.28.2 Determine whether new information supports or weakens a model, and why
GOAL: Draw an atomic sketch with the correct number of energy levels and number of electrons in each energy level
How are electrons arranged?
20
Flame Test Lab!
Purpose
To provide evidence for the presence of certain atoms within compounds.
Materials






1 Bunsen burner
1 set of tongs
1 piece of copper wire
1 penny
11 pieces of nichrome wire with a loop
1 set of 11 solutions: sodium carbonate, Na2CO3; potassium nitrate, KNO3; copper (II) nitrate, Cu(NO3)2; strontium
nitrate, Sr(NO3)2; potassium chloride, KCl; sodium chloride, NaCl; copper (II) sulfate, CuSO4; strontium chloride,
SrCl2; sodium nitrate, NaNO3; copper (II) chloride, CuCl2; potassium sulfate, K2SO4
SAFETY INSTRUCTIONS:
You will be working with flames and chemicals today.
Wear safety goggles.
Roll up long sleeves, tuck in loose clothing, and tie back long hair.
Know the location of the eye wash, fire blanket, and fire extinguisher.
Procedure and Observations
Write your observations in a table like the one below.
1.
2.
3.
4.
5.
For the solutions, follow these steps:
 Place the looped end of the wire in the solution.
 Hold the looped end in the future.
 Record the color of the flame.
 Place the wire back in the correct solution.
Note: Do not exchange wire between solutions. After you use the nichrome wire, be sure to put it back in the
solution it came from.
For the two solid copper objects, use tongs to hold each one in the flame and observe the results.
Record your observations in the data table on the following page.
Follow all clean up procedures as directed by your teacher.
Answer the analysis questions with your lab group.
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Substance Name
Formula
Flame Color
Analysis:
1. Group the substances based on the colors produced.
2. What patterns do you notice in the groupings?
3. Predict the flame color for a substance called strontium sulfate. Explain your reasoning.
4. What evidence do you have that atoms of a certain element produce a flame of a specific color?
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The evidence you just collected in the flame test is similar to observations by Niels Bohr in the early 1900s. But how can we
explain what we saw?
Bohr noted that atoms emit (give off) certain colors of light when they are heated. He theorized that electrons are located in
specific shells (represented by circles in this model). The electrons can “jump” between energy levels but cannot occupy the
space between the shells. When the electrons fall back to their original positions, they release energy in the form of light.
E.24.5 Look back at your models of the atom on p. 9. Which model(s) is(are) or weakened by the new evidence presented
above? Choose all that apply, and explain your choice(s). One choice is made for you with an example.
a. Plum pudding:
Explanation of choice: The plum pudding model has electrons randomly scattered, but the new
evidence says electrons are organized at different distances from the nucleus.
b. Proton:
c. Nuclear:
d. Solar System:
KNOW: Atomic Sketch, Valence Electrons
23
GOAL 5: Draw an atomic sketch with the correct number of energy levels and number of electrons in each.
Life on the Edge
Valence and Core Electrons
Purpose
To discover the arrangements of electrons within atoms.
Instructions
Complete the table on the handout, filling in the missing atoms. Then answer the questions.
1. How does the number of electrons change as you move from left to right across a period?
2. What do all the atoms of Group 1A elements have in common?
3. List three things that all the atoms of the elements in period 3 have in common.
4. Which atoms have two electrons in the first energy level and eight electrons in the second energy level ?
5. What happens to the electron count and the number of energy levels when you move from neon, Ne, to
sodium, Na?
6. How many energy levels of electrons does rubidium, Rb, have? How many electrons are in the outermost
energy level? Draw an energy level model of a rubidium atom.
7. Draw an energy level model of an atom with two energy level s and six electrons. What element is this? How
many electrons are in the outermost energy level?
8. Draw an energy level model of an atom with three energy levels and two electrons in the outermost energy
level l. How many total electrons does this atom have? What element is this?
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9. Look at the periodic table and the handout The energy level Model. Explain why the number of electrons in
the third energy level suddenly changes from 8 to 18 between the element calcium, Ca, and the element
gallium, Ga.
10. Summarize at least three patterns you discovered during this lesson.
11. Making Sense: Explain how you can determine the arrangement of an element’s electrons from the
element’s position in the periodic table.


Elements in the same group (column) on the Periodic Table have the ________________ of valence electrons.
Elements in the same period (row) on the Periodic Table have the _______________ of electron shells.
1A
2A
3A
4A
5A
6A
7A
8A
# of valence
electrons
Define the following terms:
Valence Electron:
Group:
Period:
25
GOAL 5: Draw an atomic sketch that represents the correct number of energy levels and number of electrons in
each energy level
Based on what you learned in the previous activity:
Number of electrons in each energy Level
Knowing the number of electrons in each energy level will help us to draw what is called an atomic sketch. An atomic sketch
is a drawing of an atom that is different from the models that we drew before because it shows the number of electrons in
each energy level. Let’s draw an atomic sketch for carbon in the space below.
First of all, we always draw a circle to represent the nucleus, and inside the circle, we write p= for the number of protons and
n= for the number of neutrons. Fill in the right numbers below.
Then, we figure out the TOTAL number of electrons: ___________
Remember, we always put only 2 electrons in the first energy level. Energy levels are represented by curves instead of
showing the whole orbit. Now that we have used 2 electrons, how many are still left? _________ Those electrons will go in
the second energy level. The second energy level can hold up to 8 electrons, as shown above.
Fill in the blanks in the atomic sketch of the Carbon atom below and then use it to help you
as your practice your own atomic sketches.
p= ___
n= ___
___
___
26
Atomic Structure and Sketch Practice
GOAL 5: Draw an atomic sketch that represents the correct number of energy levels and number of electrons in each
energy level
1) An atom of phosphorous has 15 protons and a mass number of 31. Identify the number of subatomic particles below,
and draw an atomic sketch for this element in the space below.
protons =
electrons =
neutrons =
2)
p = 16
N = 16
2
8
6
represents the atomic sketch of an element.
a) How many valence electrons does this element have? ______
b) How many total electrons does this element have? ________
c) Name the element ____________
3) The atomic number of an element is 2. The atom has a mass number of 4.
a) Draw the atomic sketch of the atom, using the sketch in question 2 as an example:
b) Name the element ___________
c) How many valence electrons does this atom have? _______
4) A certain element has 1 electron in its last shell. The last shell is the 2nd shell, and the mass number is 7.
a) Draw the atomic sketch:
b) Name the element _________________
5) The atomic number of an element is 8. The atom has a mass number of 16.
27
a) Draw the atomic sketch of the atom:
b) Name the element ___________
c) How many valence electrons does this atom have?________
6) The atomic number of an element is 17. The atom has a mass number of 35.
a) Draw the atomic sketch of the atom:
b) Name the element ___________
c) How many valence electrons does this atom have? _________
7) An atom has 3 shells, and 1 valence electron. It has a mass number of 23.
a) Draw the atomic sketch of the atom:
b) Name the element ___________
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Practice: Goals 5 Atomic Sketches
Goal 5: Draw an atomic sketch that represents the correct number of energy levels and number of electrons in each
energy level
1)
p = 12
n = 13
2
8
2
represents the atomic sketch of an element.
a) How many valence electrons does this element have? ______
b) How many total electrons does this element have? ________
c) Name the element ____________
2) The atomic number of an element is 14. The atom has a mass number of 28.
a) Draw the atomic sketch of the atom:
b) Name the element ___________
4) A certain element has 8 electrons in its last shell. The last shell is the shell 2.
a) Draw the atomic sketch:
b) Name the element _________________
5) An element has 7 electrons in its last shell. The last shell is shell 3. The mass number is 35.
a) Draw the atomic sketch:
b) Name this element _____________
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