Chemistry Module 3

1. Periodic Table: Basic Concepts
3
Periodic Table of the Elements

2. 3 Periodic Table
• Atomic number = the number of protons
• Each element has a specific number of
protons which makes it that element
• Electrons: each element initially has the
same number as protons.
• Electrons: are found in energy levels
around the nucleus

3. 3 Periodic Table
• Electrons: 1st energy level holds 2
electrons (e-). The rest of the energy
levels want 8 e-.
• Electrons: the last energy level is the
important one. Will give up or take e- to
obtain the magic number 8.
• The periodic table columns (1-18) tell you
how many e- are in the last energy level.

4. 3 Periodic Table
• Elements will either give up or take e- to
obtain stability (8)
• Elements on the left side of the table tend
to give up e-’s and elements on the right
side of the table tend to take e-’s.
• Column 18 elements have 8 in their last
energy level.

5. Periodic Table: Basic Concepts
3
Relationship of the Periodic
Table to Atomic Structure

6. Periodic Table: Basic Concepts
3
Electrons in Energy Levels—Group 16

7. Periodic Table: Basic Concepts
3
Electrons in Energy Level
The electrons in the outermost energy level are
called valence electrons.
You can also use the periodic table as a tool to
predict the number of valence electrons in
any atom in Groups
1, 2, 13, 14, 15, 16, 17, and 18.
All atoms in Group 1, like hydrogen, have one
valence electron. Likewise, atoms in Group 2
have two valence electrons.

8. Atomic Structure: Basic Concepts
3
Electrons in Energy Level
An oxygen atom has eight electrons. Two of
these fill the first energy level, and the
remaining six are in the second energy level.

9. 3 Formation of compounds
• Na (Sodium) is in column 1 and has 1
valence e-. It will give up this e- because
the energy level below it has 8.
• Cl (Chlorine) is in column 17 and has 7
valence e-’s. It will gain 1 e- to have 8.

10. Formation of Compounds: Basic Concepts
3
Electrons Can Be Transferred
• Because the chlorine atom now has an
extra electron, it has a negative charge.
• Also, because sodium lost an electron, it
now has an unbalanced proton in the
nucleus and therefore has a positive
charge.

11. Formation of Compounds: Basic Concepts
3
Formation of Water by Electron
Sharing
• The oxygen, by sharing two electrons with
two hydrogens, claims a stable octet in its
outer level.
• By this method, each atom achieves a
stable noble gas configuration.

12. Bonding and Polarity
3
• Ionic bonding: oppositely charged
• Covalent bonding: share e-

13. Chemistry
3
• Requirement:
• For each
element, hydrogen, carbon, potassium, oxyge
n, and sodium, determine the following:
• a. Does it bond ionically or covalently?
• b. How many energy levels does it have?
• c. How many valence electrons does it
have?

14. Chemistry and Matter: Additional Concepts
4
Scientific Methods
• Often, a scientist will begin with qualitative
data—information that describes
color, odor, shape, or some other physical
characteristic that relates to the five senses.
• Chemists also use numerical quantitative
data.
• A hypothesis is a possible explanation for
what has been observed.
• An experiment is a set of controlled
observations that test a hypothesis.

15. Chemistry and Matter: Additional Concepts
4
Scientific Methods
• The variable that is
changed in an experiment
is called the independent
variable.
• The variable that you
watch to see how it
changes as a result of your
changes to the independent
variable is called the
dependent variable.

16. Chemistry and Matter: Additional Concepts
4
Scientific Methods
• Many experiments also include a control,
which is a standard for comparison.
• A conclusion is a judgment based on the data
obtained in the experiment.
• If data support a hypothesis, the hypothesis is
tentatively affirmed. Hypotheses are never
proven; they are always subject to additional
research.

17. Chemistry and Matter: Additional Concepts
4
Scientific Methods
• Over time, data from many experiments can
be used to form a visual, verbal, and/or
mathematical explanation—called a
model—of the phenomenon being studied.
• A theory is an explanation that has been
supported by many experiments.
• Theories are always subject to new
experimental data and are modified to include
new data.

18. Chemistry and Matter: Additional Concepts
4
Scientific Methods
• A scientific law
describes a relationship
in nature that is
supported by many
experiments and for
which no exception has
been found.

19. Chemistry and Matter: Additional Concepts
4
Scientific Research
• Pure research is done to gain knowledge for
the sake of knowledge itself.
• Applied research is undertaken to solve a
specific problem.

20. Additional Assessment Questions
4
Question 1
Identify the dependent variable and the
independent variable in the following
experiments.

21. Additional Assessment Questions
4
Question 1a
A student tests the ability of a given chemical
to dissolve in water at three different
temperatures.
Answer 1a
independent variable:
dependent variable:

22. Additional Assessment Questions
4
Question 1b
A farmer compares how his crops grow with
and without phosphorous fertilizers.
Answer 1b
independent variable:
dependent variable:

23. Additional Assessment Questions
4
Question 2
Classify each kind of research as either pure
or applied.

24. Additional Assessment Questions
4
Question 2a
A scientist studies plants in a rain forest in
search of chemicals that might be used to treat
AIDS.
Answer 2a

25. Additional Assessment Questions
4
Question 2b
A researcher studies the effects of hormones
on the brain of a worm.
Answer 2b

26. Additional Assessment Questions
4
Question 2c
A researcher tries to develop cleaner burning
fuels to help reduce air pollution.
Answer 2c