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Chemistry
Julien
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Chapter 6: The Periodic Table
Atomic and Molecular Structure
1. The periodic table displays the elements in increasing atomic number and shows how periodicity
of the physical and chemical properties of the elements relates to atomic structure. As a basis for
understanding this concept:
a. Students know how to relate the position of an element in the periodic table to its atomic number
and atomic mass.
b. Students know how to use the periodic table to identify metals, semimetals, non-metals, and
halogens.
c. Students know how to use the periodic table to identify alkali metals, alkaline earth metals and
transition metals, trends in ionization energy, electronegativity, and the relative sizes of ions and
atoms.
f. *Students know how to use the periodic table to identify the lanthanide, actinide, and transactinide
elements and know that the transuranium elements were synthesized and identified in laboratory
experiments through the use of nuclear accelerators.
Chemical Bonds
2. Biological, chemical, and physical properties of matter result from the ability of atoms to form
bonds from electrostatic forces between electrons and protons and between atoms and molecules.
As a basis for understanding this concept:
g.*Students know how electronegativity and ionization energy relate to bond formation.
Investigation and Experimentation
1. Scientific progress is made by asking meaningful questions and conducting careful
investigations. As a basis for understanding this concept and addressing the content in the other
four strands, students should develop their own questions and perform investigations. Students
will:
d. Formulate explanations by using logic and evidence.
f. Distinguish between hypothesis and theory as scientific terms.
I. Organizing the Elements.
A. Searching for an organizing principle.
1. By the year, 1700, only 13 elements were known due to a lack of experimental techniques.
a. In 1829 J. W. Dobereiner published a classification system based on three elements with very
similar properties, which he called a triad.
b. One element in each triad had properties with values that fell in between the other two.
c. Unfortunately, not all elements could be grouped into triads.
 Chemists used the properties of elements to sort them into groups.
B. Mendeleev’s periodic table.
1. In 1869, Dimitri Mendeleev published a periodic table based on groups with similar properties.
a. Mendeleev was writing a textbook and, because there were too many elements to cover each one
individually, he put information on cards and laid the cards on a table based on his groups.
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Chapter 6 Notes from Chemistry
b. Mendeleev’s periodic table was accepted because he predicted missing elements and estimated
their properties.
 Mendeleev arranged the elements in the periodic table in order of increasing atomic mass.
C. The periodic law.
1. Mendeleev arranged his periodic table based on the atomic mass of each element.
2. The atomic mass of iodine is 126.90 and the atomic mass of tellurium is 127.60 but they wouldn’t fit
in the correct group because of their masses: he assumed that the masses were measured incorrectly.
3. In 1913, Henry Moseley determined the atomic number for each element, and the periodic table was
rearranged by atomic number, making the elements fall into the proper columns.
 In the modern periodic table, elements are arranged in order of increasing atomic number.
4. Periodic law —
D. Metals, Nonmetals, and Metalloids.
1. Groups on the periodic table are listed in three different forms.
a. American scientists use Arabic numbers and list the representative elements with A and
transitional elements with B.
b. European scientists use Roman numerals and use A through the representative elements and shift
to B to start a new octet with the last two rows of the representative elements and the p-block
elements.
c. The International Union of Pure and Applied Chemists numbers the groups from 1 to 18.
2. Metals —
3
Nonmetals —
4. Metalloids —
 Three classes of elements are metals, nonmetals, and metalloids.
II. Classifying the Elements.
A. Squares in the periodic table.
1. Each element in the periodic table is represented with its own square which can contain its symbol,
atomic number, name, average atomic, mass, electron configuration, and other information.
a. Physical states at room temperature are represented with black for solids, blue for liquids, and
red for gases.
b. Synthetic elements are represented in green or outline.
 The periodic table displays the symbols and names of the elements along with information about the
structure of their atoms.
1. Alkali metals —
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Chapter 6 Notes from Chemistry
a. The term “alkali” is from the Arabic term “al aqali” for “the ashes” where we find many of the
alkali metals.
2. Alkaline earth metals —
3. Halogens —
B. Electron configurations in groups.
 Elements can be sorted into noble gases, representative elements, transition metals, or inner transition
metals based on their electron configurations.
1. The noble gases —
Helium (He)
Neon (Ne)
Argon (Ar)
Krypton (Kr)
1s2
1s22s22p6
1s22s22p63s23p6
1s22s22p63s23p64s23d104p6
a. For the noble gases, the Group number equals the number of electrons in the highest occupied
energy level, found by adding the number of s and p electrons in the highest level with the
exception of helium.
2. The representative elements —
Lithium (Li)
Sodium (Na)
Potassium (K)
1s22s1
1s22s22p63s1
1s22s22p63s23p64s1
Carbon (C)
Silicon (Si)
Germanium (Ge)
1s22s22p2
1s22s22p63s23p2
1s22s22p63s23p64s23d104p2
a. The representative elements, the group number equals the number of electrons in the highest
occupied energy level.
C. Transition elements.
1. Groups 3 through 12 contain metals that are the elements traditionally thought of as metals, like
gold, silver, and iron.
2. Transition metal —
3. Inner transition metal —
4. Blocks of elements.
a. S-block elements are Groups 1 and 2, including helium. (American 1A and 2A, European IA and
2A)
b. P-block elements are Groups 13 through 18, not including helium. (American 3A through 8A,
European III B through VIIB)
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Chapter 6 Notes from Chemistry
c. D-block elements are Groups 3 through 12. (American 3B through 2B, European IIIA and IIB)
d. F-block elements are located below the table and are found in Group 3. (American 3B. European
IIIA)
Practice Problems
8. Use your periodic table to write the electron configurations of the following elements. (Hint: Remember
that the principal energy level number for elements in the d block is always one less than the period
number.)
a. carbon
b. strontium
c. vanadium
9. List the symbols for all the elements whose electron configurations end as follows. Each n represents an
energy level.
a. ns2np1
b. ns2np5
c. ns2np6nd2 (n+1)s2
III. Periodic Trends.
 In general, atomic size increases from top to bottom within a group and decreases from left to right
across a period.
A. Trends in atomic size.
1. Group trends in atomic size.
a. Atomic radius—
b. Group trends in atomic size show an increase as you go down a Group because each period adds
another layer of electrons.
2. Periodic trends in atomic size.
a. Periodic trends in atomic size generally decrease as one more electron and one more electron
added tend to increase nuclear charge and pull the electrons closer.
B. Ions.
1. Ion—
 Positive and negative ions form when electrons are transferred between atoms.
a. Atoms are neutral because they have equal numbers of positively charged protons and negatively
charged electrons.
b. Losing an electron upsets the balance by having more positive particles than negative particles.
c. Cation —
d. Gaining an electron upsets the balance by having more negative particles than positive particles.
e. Anion —
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Chapter 6 Notes from Chemistry
f. Ions are written with the symbol of the element with a number either followed by a negative or
positive sign, depending on the amount of charge of the ion.
C. Trends in ionization energy.
1. Ionization energy —
 First ionization energy tends to decrease from top to bottom within a group and increase from left to right
across a period.
2. The energy needed to remove the second and third electrons is called the second ionization energy
and the third ionization energy.
3. Ionization energy increases dramatically when electrons are removed from filled sublevels and
shows a notable increase when electrons are removed from half-filled sublevels.
Ionization Energies of First 20 Elements (KJ/mol)
Symbol
First
Second
Third
H
1312
He (noble gas)
2372
5247
Li
520
7297
11810
Be
899
1757
14840
B
801
2430
3659
C
1086
2352
4619
N
1402
2857
4577
O
1314
3391
5301
F
1681
3375
6045
Ne (noble gas)
2080
3963
6276
Na
496
4565
6912
Mg
738
1450
7732
Al
578
1816
2744
Si
786
1577
3229
P
1012
1896
2910
S
999
2260
3380
Cl
1256
2297
3850
Ar (noble gas)
1520
2665
3947
K
419
3069
4600
Ca
590
1146
4941
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Chapter 6 Notes from Chemistry
D. Trends in ionic size.
1. In reactions between metals and nonmetals, metals tend to lose electrons and become positive and
nonmetals tend to gain electrons and become negative.
2. Cations (metals, positive) lose electrons and therefore become smaller in size.
3. Anions (nonmetals, negative) gain electrons and become larger in size
TREND: Atoms tend to get smaller as you move up and to the right of
the periodic table. Cations are smaller than their corresponding atom;
anions are larger than their corresponding atom.
 Cations are always smaller than the atoms from which they form. Anions are always larger than the
atoms from which they form.
E. Trends in Electronegativity.
1. Electronegativity —
2. Metals tend to be larger atoms with one or two outside electrons that can be attracted away from the
metallic nucleus because of its distance from the nucleus.
3. Nonmetals tend to be small with many outside electrons that are held closely to the nucleus and are
harder to remove electrons making it easier to attract electrons.
 In general, electronegativity values decrease from top to bottom within a group. For representative
elements, the values tend to increase from left to right across a period.
F. Summary of trends.
1. The nuclear charge increases as you move down and to the right on the periodic chart but the
shielding of the nucleus increases as you go down but remains constant as you move to the right.
2. This makes the size decrease as you move across the table and increase as you move down.
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Chapter 6 Notes from Chemistry
 The trends that exist among these properties can be explained by variations in atomic structure.
TREND: Electronegativity tends to increase as you move up and to the
right on the periodic table.
PRACTICE FOR THE TEST:
Standardized Test Prep, page 185
Internet Practice:
http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cdk&wcsuf
fix=0000Click on the arrow above the picture of your Chemistry book.
Your grades can be accessed through http://web.me.com/ejulien/Mr._Juliens_Homepage/Welcome.html
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Chapter 6 Notes from Chemistry