Download CHEM A Midterm Review

CHEM A
2015 Midterm
Review
Need more practice?
Not sure how to study?
Reviewing for the Midterm?
The following worksheets are organized by learning targets, so
you can pick and choose which to complete or do them all!
Matter Lab Packet Review:
1. Define each of the following terms:
matter:
volume:
mass:
density:
2. Standard metric units: for length
and for mass
.
for volume
3. What is the correct volume as shown on the following graduated cylinders?
a.
.
mL
b.
.
mL
a.
.
g
b.
.
g
4. What is the correct volume as shown on the following balances?
5. A student was told to find the density of a solid object. The mass of the object was found using a
balance. The volume was determined using water displacement. Below is the data collected:
Volume of water and object in graduate 37.55 mL
Volume of water in graduate
31.83 mL
Calculate the density of the solid.
Mass of object 10.405 g
Density of an Unknown Liquid
PURPOSE: For Determine what it is by calculating its density.
LAB:
A student filled a buret with unknown liquid and made sure the original reading of the buret was 0.0 mL. She
measured the mass of an empty beaker and then put some of the unknown liquid into the beaker. She
recorded the new buret reading and measured the mass of the beaker and liquid. Without emptying the
beaker she added more liquid to the beaker. She read and recorded the new buret reading and measured the
mass of the beaker and liquid sample. She repeated this process twice more so that she had four values for
volume and mass of the unknown liquid. Her data:
Sample 1
mass of beaker and liquid
mass of beaker
mass of liquid
Sample 3
39.65g
28.94g
______
mass of beaker and liquid __57.51 g__
mass of beaker
__________
mass of liquid
__________
volume of liquid (buret reading)
15.20 mL
volume of liquid (buret reading)
40.00 mL___
Sample 2
Sample 4
mass of beaker and liquid __51.04 g__
mass of beaker
__________
mass of liquid
__________
mass of beaker and liquid __62.99 g__
mass of beaker
__________
mass of liquid
__________
volume of liquid (buret reading)
29.80 mL
volume of liquid (buret reading)
49.00 mL
Use the grid on the BACK of this sheet to graph the student’s data. Be sure to put scales and labels on each
axis and give your graph a title.
**Show a neat calculation for the slope of your graph, including labels BELOW:
The student was told the unknown liquid was one of the following:
 cyclobutane (density = 0.720 g/mL)
 ethanol (density = 0.789 g/mL)
 2-octanol (density = 0.822 g/mL).
Based upon the data and your calculation, what was the identity of the student’s unknown?
Title:
Periodic Table Unit Learning Targets
Learning Targets 1.1, 1.5 and 1.12 will be assessed on quizzes, but not the unit test.
1.1 I can write the names and symbols of the elements in columns 1A – 4A on the periodic table.
1.5 I can write the names and symbols of the elements in columns 5A- 8A on the periodic table.
1.12 I can write the names and symbols of selected transition metals, lanthanides and actinides
(1B-12B) on the periodic table.
LT 1.2 I can describe how Mendeleev and Moseley organized the periodic table into groups with
similar properties.
LT 1.3 I can label and describe the major groups (families) of the periodic table: alkali metals,
alkaline metals, transition metals, halogens, noble gases, metals, non-metals and metalloids
LT 1.4 I can describe the charge and location of protons, neutrons, and electrons within the
nucleus and shells of an atom.
LT 1.6 I can calculate the number of protons, electrons and neutrons if given the mass and atomic
number of an element.
LT 1.7 I can describe the relationship between neutral atoms and ions of the same element.
LT 1.8 I can explain the relationship between isotopes of the same element.
LT 1.9 I can calculate the number of protons, electrons and neutrons in ions and isotopes of the
same element.
LT 1.10 I can explain the difference between mass number and average atomic mass.
LT 1.11 I can calculate average atomic mass.
Fill in the Blanks Review
Learning Targets Addressed
1.2 I can describe how Mendeleev and Moseley organized the periodic table into groups with similar properties.
1.3 I can label and describe the major groups (families) of the periodic table: alkali metals, alkaline metals, transition
metals, halogens, noble gases, metals, non-metals and metalloids
Directions: Fill in the blanks on the right with the information in the chart below.
Word List
actinide series
metal
alkali metal
metalloid
alkaline earth metal
Moseley
atomic mass
noble gas
atomic number
nonmetal
family
period
group
periodic law
halogen
periodic table
lanthanide series
transition element
1. ____________________
2. ____________________
3. ____________________
4. ____________________
5. ____________________
6. ____________________
Dmitri Mendeleev developed a chart-like arrangement of the elements
7. ____________________
called the __(1)__. He stated that if the elements were listed in order of increasing
__(2)__, their properties repeated in a regular manner. He called this the __(3)__
8. ____________________
of the elements. The arrangement used today, devised by __(4)__, differs from
9. ____________________
that of Mendeleev in that the elements are arranged in order of increasing __(5)__.
10. ____________________
Each horizontal row of elements is called a(n) __(6)__. Each vertical column is
11. ____________________
called a(n) __(7)__, or, because of the resemblance between elements in the same
12. ____________________
column, a(n) __(8)__.
In rows 4 through 7, there is a wide central section containing elements,
13. ____________________
each of which is called a(n) __(9)__. Rows 6 and 7 also contain two other sets of
14. ____________________
elements that are listed below the main chart. These are called the __(10)__ and
15. ____________________
the __(11)__, respectively. Each of these elements, as well as those in the first two
16. ____________________
columns at the left end of the chart, is classified as a(n) __(12)__. Each of the
elements at the right side of the chart is classified as a(n) __(13)__. Each of the
elements between these two main types of elements, having some properties in
common with each, is called a(n) __(14)__.
Each of the elements in Group 1A is called a(n) __(15)__. Each of the
elements in the Group 2A is called a(n) __(16)__. Each of the elements in Group
7A is called a(n) __(17)__. Each of the elements in Group 8A is called a(n)
__(18)__.
17. ____________________
18. ____________________
Directions:
1. Go to mrscrane.wiki.farmington.k12.mi.us
2. Following the links to “Chemistry A” and “Periodic Table Unit”
3. Follow the link to “Groups of the Periodic Table”
4. When you get to the website, read and answer the following questions.
1. How are the families of the periodic table like real life families?
2. What is the definition of a metal? __________________________________________________________________
3. What is common table salt made of? ____________________________ and _____________________________
4. What is an unusual property of the alkaline earth metals?
________________________________________
5. Why don’t noble gases react with other elements?
_________________________________________________
6. What does the world “halogen” mean?
______________________________________________________________
7. What is the definition of a non-metal?
______________________________________________________________
8. What is the most reactive element? __________________________
9. Label the periodic table below with: lanthanide series, actinide series, transition metals,
alkali metals, alkaline metals, halogens, noble gases.
Basic Atomic Structure Review
Learning Target Addressed:
1.4 I can describe the charge and location of protons, neutrons, and electrons within the nucleus and shells of an atom.
The periodic table is, in many ways, the world’s greatest cheat sheet. The periodic table lists all of the elements (simple
substances that make up more complex materials) like gold, silver, tin, lead and mercury. It also provides lots of
information about these elements. The table was created a long time ago by a guy named Dmitri Mendeleev who,
probably like you, did not want to memorize tons of information. He organized the elements by mass. That worked pretty
well to group elements with similar properties together. Soon after a guy named Henry Moseley realized that each
element has a specific number of protons. We call this the atomic number of the element. When he rearranged the
periodic table by atomic number the elements grouped into columns with similar properties.
Questions:
1.
Who created the first periodic table?
2.
What is an element?
3.
What are the vertical (up and down) columns of the periodic table called? ___________________
4.
What are the horizontal (back and forth) rows of the periodic table called? __________________
5.
Which elements have similar properties, those in the same period or in the same family? _________
6.
How did Mosley improve the organization of the periodic table?
What makes up each element?
The parts that make up an element are called sub-atomic particles. There are three basic sub-atomic particles that we
will talk about in chemistry, they are called protons, neutrons and electrons. Each proton has one positive charge of
electricity (+1). Each electron has one negative charge of electricity (-1). Neutrons are neutral, which means they do not
have a charge.
7.
What is a sub-atomic particle?
8.
What is the difference between a proton, a neutron and an electron?
Here is a close-up of the periodic table symbol
Here is a close-up of the element carbon if we
for carbon, an element that is very common and
could see it under a very powerful microscope:
we will study about this trimester:
KEY
Atomic
Number
p = proton
n = neutron
Mass
Number
= electron
Nucleus
9.
Are the protons and neutrons found inside or outside the nucleus?
10. Are the electrons found inside or outside the nucleus?
The electron cloud is
made of “shells” that hold
the electrons. Carbon has
2 shells and is in the 2nd
row of the periodic table.
11. How many electrons does carbon have?
12. How many protons does carbon have?
13. How many neutrons does carbon have?
14. What is the total positive charge of carbon?
15. What is the total negative charge of carbon?
These + and – charges
“cancel out” making a
neutral carbon atom.
Practice with Ions
Learning Target Addressed:
1.7 I can describe the relationship between neutral atoms and ions of the same element.
Remember: The charge on an ion will involve a number and a sign. The number will always be the
number of electrons involved, e.g., loss of two electrons is +2. The sign will be positive if electrons
(negatives) are lost and negative if electrons are gained.
I. Determine the following charges
1. An atom having lost three electrons
2. An atom having lost five electrons
3. An atom having gained one electron
________
When you get rid of
“negatives” it makes
you more positive.
Same for atoms!
________
________
4. An atom having gained two electrons ________
5. An atom having lost four electrons
________
II. Determine the charges on the following elements based on their locations on the
periodic table. Then circle if each ion is a cation or an anion.
1. oxygen ______ Circle one: CATION or ANION
2. lithium______ Circle one: CATION or ANION
3. boron______ Circle one: CATION or ANION
4. fluorine______ Circle one: CATION or ANION
5. arsenic______ Circle one: CATION or ANION
6. bromine______ Circle one: CATION or ANION
7. xexon______ Why don’t noble gases form cations or anions?
III. Fill in the table below:
Ion
O-2
K+1
N-3
S-2
Sr+2
Al+3
Atomic #
Mass #
# of
protons
# of neutrons
# of electrons
Practice with Isotopes
Learning Target Addressed
1.8 I can describe the relationship between isotopes of the same element.
Isotopes are atoms of the same element with different masses (or weights) due to different numbers of
neutrons in their nuclei. All atoms of the same element must have the same number of protons (and thus the same number
of electrons) which is equal to the atomic number. However, atoms of the same element can have different numbers of
neutrons and thus a different mass number. The difference in mass does not influence the chemical behavior. Valence
electrons are what determine chemical behavior.
Hydrogen has three isotopes. The most abundant isotope is ordinary hydrogen-1. A second stable isotope is hydrogen-2 and
the third isotope is the radioactive hydrogen-3. The Bohr diagrams for the isotopes of hydrogen are shown below. Notice
that only the mass number and number of neutrons are different.
Hydrogen-1
Hydrogen-2
Hydrogen-3
K
K
K
1
2
3
1p
1p
1p
1H
1H
1H
1n
2n
1e
1e
1e
1. What is an isotope? _____________________________________________________________
___________________________________________________________________________
2. What does the number next to isotopes signify (ie: Carbon 12 vs. Carbon 13)? _______________
___________________________________________________________________________
3. How can you tell isotopes apart in lab? ______________________________________________
___________________________________________________________________________
4. Here are three isotopes of an element:
12
6 C
13
6
C
14
6
C
a. The element is: __________________
b. The number 6 refers to the _________________________
c. The numbers 12, 13, and 14 refer to the ________________________
d. How many protons and neutrons are in the first isotope? _________________
e. How many protons and neutrons are in the second isotope? _________________
f.
How many protons and neutrons are in the third isotope? _________________
5. Write the symbols for the isotopes of uranium with the following numbers of neutrons:
a. 142 neutrons
b. 143 neutrons
c. 146 neutrons
6. Complete the following chart:
Isotope name
Uranium-235
Uranium-238
Boron-10
Boron-11
Carbon – 12
Carbon – 14
Tin – 119
Tin – 120
Lithium – 7
Sodium – 23
Atomic #
Mass #
# of
protons
# of neutrons
# of electrons
The Nucleus: Crash Course in Chemistry #1
Learning Targets Addressed:
LT 1.4 I can describe the charge and location of protons, neutrons, and electrons within the nucleus and
shells of an atom.
LT 1.6 I can calculate the number of protons, electrons and neutrons if given the mass and atomic number of
an element.
https://www.youtube.com/watch?v=FSyAehMdpyI (10:12)
The video above should help you answer the following questions:
1. What is “stuff” made of?
2. What are atoms?
3. What are the three sub-atomic particles?
4. What is atomic number AND why is it important?
5. True or False: If the number of neutrons in a silver atom changes, then the atomic
number changes.
6. Do all silver atoms have the same number of neutrons? Explain!
7. How to do you calculate the relative atomic mass of silver?
8. What are the masses of the two isotopes (forms) of silver?
9. LABEL mass and atomic number on the chemical symbol of
silver to the right:
Practice Calculating Average Atomic Mass
Learning Target Addressed: 1.11 I can calculate average atomic mass.
The atomic masses (or atomic weights) on the periodic table are the average of all the isotopes but it is not
a straight average. The atomic masses on the periodic table are the averages of all the isotopes based upon
abundance.
For example, consider element X:
60% mass 40 amu,
30% mass 42 amu
10% mass 44 amu,
then the periodic table mass would be calculated:
average mass based upon relative abundance
.60 x 40 amu = 24.0 amu
.30 x 42 amu = 12.6 amu
.10 x 44 amu = 4.4 amu
= 41.0 amu
Calculate the average atomic mass for the following isotopes.
Element
Mass of
Abundance
Atomic Mass Based Upon Relative Abundance
Isotope
1. Nitrogen
N-14
14.0031 amu
99.64 %
N-15
15.0001 amu
0.36 %.
2. Magnesium
Mg-24
Mg-25
Mg-26
23.9850 amu
24.9858 amu
25.9826 amu
78.99 %
10.00 %
11.01 %
3. Neon
Ne-20
Ne-21
Ne-22
19.992 amu
20.994 amu
21.991 amu
90.51%
0.27%
9.22%
4. Chromium
Cr-50
Cr-52
Cr-53
Cr-54
49.9461 amu
51.9405 amu
52.9407 amu
53.9389 amu
4.35 %
83.79%
9.50%
2.36 %
Periodic Table Short Answers:
1. Explain how Moseley improved upon Mendeleev’s periodic table.
2. What are the names for groups 1A, 2A, 7A and 8A on the periodic table?
3. Chlorine is a reactive, non-metal that is a gas at room temperature. Predict 2 other elements that would
have similar characteristics.
4. Which subatomic particles (protons, neutrons, electrons) affect the mass of an atom?
5. Which subatomic particles affect the charge of an atom? EXPLAIN!
6. What is an ion? Provide both a definition AND an example.
7. What is the difference between a mass number and an average atomic mass? Which is listed on the
periodic table of elements?
8. What is an isotope? Provide BOTH a definition AND an example.
Atomic Structure Learning Targets
2.1 I can describe how society’s understanding of atomic structure has
changed over time.
2.2 I can draw Bohr Diagrams for the first 20 elements.
2.3 I can draw Dot Diagrams for neutral atoms.
2.4 I can create orbital diagrams to show the placement of electrons in suborbitals for the first 36 elements.
2.5 I can create complete electron configurations for the first 36 elements.
2.6 I can create noble gas electron configurations for the first 36 elements
2.7 I can compare and contrast the information provided in Bohr Diagrams,
Dot Diagrams and Electron Configurations.
Bohr Diagram Practice
Learning Target Addressed: 2.2 I can draw Bohr Diagrams for the first 20 elements.
Directions: Write Bohr Diagrams for each of the following atoms:
aluminum (Al)
sulfur (S)
oxygen (O)
calcium (Ca)
Dot Diagram Practice
Learning Target Addressed:
2.3 I can draw Dot Diagrams for neutral atoms.
2.7 I can compare and contrast the information provided in Bohr Diagrams, Dot Diagrams and Electron
Configurations
1
8
H
2
3
4
5
6
7
Li
Be
B
C
N
O
F
He
Ne
Follow Up Questions:
Compare and Contrast Bohr Diagrams and Dot Diagrams. What information do Bohr Diagrams
provide that a Dot Diagram does not include?
____________________________________________________________________________________
____________________________________________________________________________________
Helium has 2 valence electrons and Neon has 8 valence electrons. But what do they both have in
common?
__________________________________________________________________________________
__________________________________________________________________________________
Extra Notes on Electron Diagrams-Orbitals, Electron Configurations
and Noble Gas Configurations
Learning Targets Addressed:
2.4 I can create orbital diagrams to show the placement of electrons in suborbitals for the first 36 elements.
2.5 I can create complete electron configurations for the first 36 elements
2.6 I can create noble gas electron configurations for the first 36 elements
One way to approach the very abstract task of filling electron orbitals is to use an analogy to make it a bit more
concrete. Imagine you are the landlord of a very strange apartment building. Your job is to fill the apartments in the
building in the most efficient way possible. You are required by the owner of the building to fill the rooms in a certain way.
The rules are summarized in the table on the next page.
In the building the different floors are like the different orbitals in an atom. The orbitals are numbered starting from
one, just like the floors in an apartment. Each room corresponds to one suborbital: one box on the diagram above.
The rooms can hold to more than two electrons (two people) each. In each room only a man and a woman may be
paired together. In the strange world of quantum mechanics there are no same-gender room mates.
Apartment House Rules
Electron Rules
From the Bottom Up: Rooms must be filled from the ground Aufbau Principle: the electrons fill the available orbitals
floor up. Fill the one room on the first floor before starting to from lowest energy to highest energy. In the ground state all
put new tenants on the second floor. Then fill the s room
the electrons are in the lowest possible energy level.
before the p rooms. At higher floors the order might change a
bit.
Singles First: the owner of the building wants to have the
tenants spread out as much as possible. For that reason
singles are placed in rooms before couples. If couples must
be placed into a room then all of the other rooms on that floor
must already have a single in them.
Hund’s Rule: The electrons must be placed into the orbitals
in such a way that no pairs are put together unless absolutely
necessary. That is, single electrons must be placed into boxes
first and then paired up if necessary.
Opposite Gender Only: When two people are placed in a
room they must be of opposite genders. No men may room
together and no women may room together. This is an
arbitrary rule on the part of the owners: we all know this isn’t
how it works in the real world.
Pauli Exclusion Principle: Electrons come in two varieties
based on the direction they are ‘spinning’. There is an Up
spin and a Down spin. Up and Down spins are always paired
together and Up-Up or Down-Down combinations are not
allowed. No two electrons can ever be in the same place at
the same time.
Here is an example of the rooms in the apartment house
having been filled in by the rules. The element Sulfur has 16
electrons and starting from the bottom up you place two (1
Up and 1 Down) in the 1s suborbital.
Next, electrons are placed in each of the 2p suborbitals
until there is one in each suborbital. Then the rest of the
electrons are filled into the 2p suborbitals. After that the 3s
suborbital is filled and then the 3p. Electrons are placed in
the boxes of the 3p suborbitals one at a time until there is
one in each suborbital. After that the remaining electron is
placed as part of a pair in the first 3p box.
The electron configuration of Sulfur is 1s2 2s2 2p6 3s2 3p4. In that notation 1s2 means orbital1, s-type suborbital, 2 e-; 2s2
means orbital 2, s-type suborbital, 2 e-; 2p6 means orbital 2, p-type suborbital, 6 e-; 3s2 means orbital 3, s-type
suborbital, 2 e-; and, finally, 3p4 means orbital 3, p-type suborbital, 4 e-.
“Reading” the Periodic Table
Look at the electron configurations of Oxygen and Sulfur. Notice that in both cases the last
1s2 2s2 2p4
Oxygen
suborbitals to fill are p suborbitals. Notice also that there are 2 electrons in an s
suborbital and 4 electrons in p orbital for both Oxygen and Sulfur.
1s2 2s2 2p6 3s2 3p4
Sulfur
For these reasons Oxygen and Sulfur belong to the p-block of elements in the periodic
table. In fact, all of the elements from Groups 13 to 18 are part of the p-block. All of the elements in this block fill a set
of p suborbitals last and all of them have their valence electrons in s and p suborbitals.
Here you can finally understand the reason that having eight electrons is so important. Each s orbital holds 2
electrons and each p orbital holds 6 electrons. Together they can hold the eight electrons it takes to finish off the
suborbitals and make the valence shell full.
Other sections of the periodic table are also known by the type of suborbital that fills last in that section. In Groups 1 and 2
the s suborbitals are filling. In Groups 3 through 12 the d suborbitals are the last to be filled. Incidentally, one
important fact is that the 4s suborbital fills before the 3d suborbitals start to fill. This is because the 4s suborbital is actually
slightly lower in energy than the 3d suborbitals. You will not be much concerned with any suborbitals higher than the 4s
suborbital since there are some interesting but complicated exceptions to the rules when it comes to filling the 3d suborbitals.
Noble Gas (Abbreviated) Electron Configurations
As we get to larger elements we notice the electron configuration becomes tediously long and repetitive so
obviously there must be some way to abbreviate configurations. The system for abbreviating involves comparing the
electron structure of the atom you are considering with that of a noble gas. Since the noble (or inert) gases have the
most stable electron arrangements we use them for a reference. An element is abbreviated by comparing its structure to
the noble gas at the end of the preceding period of the periodic table. You abbreviate the element's configuration by
indicating the appropriate noble gas plus all of the additional electrons in the element you are considering.
Example: Show the abbreviated configuration for chlorine. Note that the noble gas neon precedes chlorine.
35
20
The complete configuration for chlorine is 17
Cl 1s22s22p63s23p5 since neon has the configuration
10 Ne
1s22s22p6 this sequence can be replaced by [Ne], so the abbreviated configuration for chlorine is
35
17
Cl [Ne]3s23p5
Electron Configuration Practice
Learning Targets Addressed:
2.5 I can create complete electron configurations for the first 36 elements
2.6 I can create noble gas electron configurations for the first 36 elements
Directions: Please write the complete electron configuration AND noble gas configuration for the elements listed
below:
HINTS!!
 Use the boxes for arrow orbital diagrams below IF it helps you to create the electron configurations
 Remember what the largest exponent in each level can be: s = 2 p = 6 d = 10
 For noble gas configurations: Put the noble gas before the element in [ ] with the highest s suborbital and
anything after that if there is anything.
Element (Symbol)
Complete Configuration
Noble Gas Configuration
Sulfur (S)
Oxygen (O)
Potassium (K)
Beryllium (Be)
OPTIONAL ARROW DIAGRAMS TO HELP WITH THE CONFIGURATIONS :
Atomic Structure Worksheet
Learning Targets Addressed:
2.3 I can draw Dot Diagrams for neutral atoms.
2.4 I can create orbital diagrams to show the placement of electrons in suborbitals for the first 36 elements.
2.5 I can create complete electron configurations for the first 36 elements
2.6 I can create noble gas electron configurations for the first 36 elements
2.7 I can compare and contrast the information provided in Bohr Diagrams, Dot Diagrams and Electron
Configurations
For each element listed you are to draw or write the following: the symbol, the complete electron
configuration, the noble gas configuration, the arrow orbital diagram and the dot diagram
Nitrogen
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Sulfur
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Helium
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Aluminum
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Phosphorus
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Iron
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Copper
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Arsenic
Symbol
Complete electron configuration
Arrow orbital diagram
Noble Gas configuration
Dot Diagram
Atomic Structure Short Answers
1. Learning Target 2.7
What information does a Bohr Diagram provide that neither a dot diagram nor an electron
configuration includes?
2. Learning Target 2.7
Although dot diagrams are easier to write than electron configurations, what extra information
does the electron configuration provide?
3. Learning Target 2.7
Why do people often prefer to use noble gas configurations instead of complete electron
configurations?
4. Learning Target 2.7
If a nuclear physicist was trying to show the change in the nucleus of an atom during a nuclear
explosion, which kind of diagram would he/she most likely use AND WHY?
5. Learning Target 2.7
Which type of diagram would be most useful in order to explain the movement of valence
electrons from one atom to another?
6. Learning Target 2.7
Why do we need so many different diagrams of the atom (Bohr, dot, orbital, electron
configuration, noble gas configuration)?