Download Honors Chemistry Name Julien Period _____ Date Atoms and

Honors Chemistry
Julien
Name _________________________
Period _____ Date _______________
Atoms and Elements
Chapter 4
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.
e. Students know the nucleus of the atom is much smaller than the atom yet contains most of its mass.
h.*Students know the experimental basis for Thomson’s discovery of the electron, Rutherford’s nuclear
atom, Millikan’s oil drop experiment, and Einstein’s explanation of the photoelectric effect.
I. Elements and Symbols.
Read Section 4.1 in your eText! Given the name of an element, I will write its correct
symbol; from the symbol, write the correct name.
A. Chemical Symbols.
1. Chemical Symbols —
2. The first letter is always capitalized and the second letter is always lower case.
a. This allows us to differentiate Co (cobalt) from CO (carbon monoxide).
b. The names of elements come from ancient names and so their symbols reflect the ancient
names.
Do The Element Names, Symbols, and Atomic Numbers Tutorial!
Problem 1: What are the chemical symbols for the elements silicon, selenium, and silver?
Problem 2: What are the names of the elements with the chemical symbols Mg, Al, and F?
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Chapter 4 Notes from Basic Chemistry
You are now able to do problem 4.2 in the first homework assignment and problem 4.58 in
the second homework assignment!
II.
The Periodic Table.
Read Section 4.2 in your eText! I will use the periodic table to identify the group and the
period of an element and decide whether it is a metal, a metalloid, or a nonmetal.
A. The Periodic Table.
1. Russian scientist, Dimitri Mendeleev, in 1872, arranged the sixty known elements at the time
by groups that shared similar properties.
2. He then arranged them by increasing atomic masses.
3. The Periodic Table—
B. Periods and Groups.
1. Period—
2. Each row, counted from the top to the bottom, represents a period on the Periodic Table.
3. The first row has two elements; the second has eight as does the third.
4. The fourth and fifth rows have eighteen, while the sixth and seventh have thirty-two
elements.
5. Group (or family)—
6. Representative elements (A)—
7. Transition elements (B)—
Do The Elements and Symbols in the Periodic Table Tutorial!
C. Classification of groups
1. Alkali metals—
a. These are soft, silvery metals with low melting points that react vigorously with water.
2. Alkaline earth metals—
a. These are similar to the alkali metals but are less reactive.
3. Halogens—
a. These elements are highly reactive and react with most elements.
4. Noble gases—
a. These elements are quite unreactive and seldom found in combination with other
elements.
Problem 3: Strontium is an element that gives a brilliant red color to fireworks.
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Chapter 4 Notes from Basic Chemistry
a. In what group is strontium found?
b. What is the name of this chemical family?
c. In what period is strontium found?
d. For the same group, what element is in Period 3?
e. What alkali metal, halogen, and noble gas are in the same period as strontium?
D. Metals, Metalloids, and Nonmetals.
1. Elements to the left of the zigzag line are metals, except for hydrogen, and elements to the
right of the zigzag line are nonmetals.
2. Metals—
3. Nonmetals—
4. Metalloids—
Problem 4: Give the symbol of the element represented by each of the following:
a. Group 5A (15), Period 4
b. a noble gas in Period 6
c. a metalloid in Period 2
You are now able to do problems 4.8 and 4.12 in the first homework assignment and
problems 4.54, 4.56, 4.60, 4.62, and 4.66 in the second homework assignment!
III. The Atom.
Read Section 4.3 in your eText! I will describe the electrical charge and location in an atom
for a proton, a neutron, and an electron.
A. Atom—
1. Greek historian and philosopher, Democritus, reasoned that substances could be divided until a
point where they could no longer be divided, calling this particle, atmos.
2. Democritus was basically ignored until 1808 when the concept of an atom became a theory.
Do The Atoms and Isotopes Self Study Activity and The Anatomy of Atoms Tutorial!
B. Dalton’s Atomic Theory
1. John Dalton’s proposal for the atom.
a. All matter is made up of tiny particles called atoms.
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Chapter 4 Notes from Basic Chemistry
b. All atoms of a given element are identical to one another and different from atoms of other
elements.
c. Atoms of two or more different elements combine to form compounds. A particular
compound is always made up of the same kinds of atoms and the same number of each kind
of atom.
d. A chemical reaction involves the rearrangement, separation, or combination of atoms.
Atoms are never created or destroyed during a chemical reaction.
2. Dalton’s proposals have been altered as we have discovered more about the atom.
3. Using a Scanning Tunneling Microscope (STM) we can create images of crystals made of atoms
that show an orderly arrangement of atoms but is far from detailed.
C. Electrical Charges in an Atom.
1. By the end of the 1800s, experiments with electricity showed us that atoms were not solid
spheres but made of smaller particles.
2. Subatomic particles—
3. Electrical charges can be positive or negative and unlike charges attract where like charges repel.
D. Structure of the Atom.
1. J. J. Thompson, in 1897, used a cathode ray tube to produce a stream of particles called a cathode
ray.
2. The particles were attracted to a positively charge electrode.
3. Electrons—
4. Protons—
5. Thompson proposed a “plum-pudding” model for the atom where the electrons and protons were
randomly distributed in the atom.
6. Ernst Rutherford performed an experiment where he shot gold foil with alpha particles and
discovered that a very few came straight back, some deflected slightly, and most went straight
through.
7. He concluded that the center of the atom was very dense and very small and that the positive
charge was concentrated in the center of the atom.
8. Nucleus—a small, positively charged region at the center of the atom.
9. Scientists found a way to measure the mass of the nucleus and concluded that the nucleus must
contain a neutral particle.
10. Neutron—
E. Mass of the Atom.
1. All of the subatomic particles are extremely small and have extremely small masses.
a. Protons and neutrons have masses around 1.673 x 10–24 g and the electron has a mass of
about 9.110 x 10–28 g.
b. Atomic mass unit (amu)—
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Chapter 4 Notes from Basic Chemistry
Particle
Proton
Neutron
Electron
Relative
Charge
Symbol
Mass (g)
Mass (amu)
Location in
Atom
Problem 5: Give the symbol, electrical charge, and location of a proton in an atom:
a. symbol:
b. relative charge:
c. location:
You are now able to do problem 4.20 in the first homework assignment and problems 4.47,
4.48, and 4.70 in the second homework assignment!
IV. Atomic Number and Mass Number.
Read Section 4.4 in your eText! Given the atomic number and the mass number of an atom,
I will state the number of protons, neutrons, and electrons.
A. Atomic Number—
atomic number = number of protons in an atom
1. An atom is electronically neutral which means that the number of protons in an atom is equal to
the number of electrons.
Do The Atomic Number and Mass Number Tutorial!
Problem 6: Consider an atom that has 79 electrons.
a. How many protons are in its nucleus?
b. What is its atomic number?
c. What is its name, and what is its symbol?
B. Mass Number—
mass number = number of protons + number of neutrons
1. To determine the number of neutrons in an element, you simply subtract the atomic number from
the mass number.
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Chapter 4 Notes from Basic Chemistry
Name of
Element
Symbol
Al
Atomic
Number
Mass
Number
27
Number of
Protons
12
Potassium
16
Number of
Neutrons
Number of
Electrons
12
20
15
56
26
Problem 7: How many neutrons are in the nucleus of a bromine atom that has a mass number of 80?
You are now able to do problems 4.28 and 4.30 in the first homework assignment!
V. Isotopes and Atomic Mass.
Read Section 4.5 in your eText! I will give the number of protons, and neutrons in an isotope
of an element; calculate the atomic mass of an element.
A. Atoms and Isotopes.
1. Isotopes—
2. The differences between isotopes give them different masses but the chemical properties are the
same.
3. Atomic symbol—
4. Isotopes are referred to by its name or symbol followed by the mass number.
a. Carbon–12 has six protons and six neutrons.
b. Carbon–13 has six protons and eight neutrons and is also radioactive.
Problem 8: Write a symbol for each of the following isotopes:
a. a nitrogen atom with eight neutrons
b. an atom with 20 protons and 22 neutrons
c. an atom with mass number 27 and 14 neutrons
B. Atomic Mass.
1. Atomic mass—
a. Most elements exist as isotopes and each as a different percentage of the total amount of the
overall element.
C. Calculating Atomic Mass.
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Chapter 4 Notes from Basic Chemistry
1. Chlorine–35 makes up 75.76% of any sample of chlorine and chlorine–37 makes up the other
24.24%
2. The average mass is calculated using the percentage of each isotope and its mass.
Atomic mass of Cl = mass Cl-35 x
Cl–35%
Cl–37%
+ mass Cl–37 x
100%
100%
Chlorine–35
34.97 amu
x
75.76
100
=
26.49 amu
Chlorine–37
36.97 amu
x
24.24%
100%
=
8.962 amu
=
35.45 amu
Atomic mass of Cl
Do The Atomic Mass Calculations Tutorial!
Problem 9: There are two naturally occurring isotopes of boron. The isotope 105 B has a mass of 10.01 amu
with an abundance of 19.80%, and 115 B has a mass of 11.01 amu with an abundance of 80.20%.
What is the atomic mass of boron?
You are now able to do problems 4.32, 4.33, 4.36 and 4.40 in the first homework assignment
and problems 4.44, 4.49, 4.51, 4.52, 4.70, 4.72, 4.74, 4.80, 4.83 and 4.84 in the second
homework assignment!
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Chapter 4 Notes from Basic Chemistry