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End Show© Copyright Pearson Prentice Hall
Distinguishing Among Atoms >
Slide 1 of 52
Atomic Mass
Atomic Mass
How do you calculate the atomic mass of an element?
4.3
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Slide 2 of 52
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>Distinguishing Among Atoms Atomic Mass
It is useful to to compare the relative masses of atoms to a standard reference isotope. Carbon-12 is the standard reference isotope. Cabon-12 has a mass of exactly 12 atomic mass units.
An atomic mass unit (amu) is defined as one twelfth of the mass of a carbon-12 atom.
4.3
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Slide 3 of 52
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>Distinguishing Among Atoms Atomic Mass
Some Elements and Their Isotopes
4.3
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Slide 4 of 52
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>Distinguishing Among Atoms Atomic Mass
The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element.
A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.
4.3
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Slide 6 of 52
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Practice Problems
for Conceptual Problem 4.3
for Conceptual Problem 4.3
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Slide 7 of 52
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>Distinguishing Among Atoms Atomic Mass
For example, carbon has two stable isotopes:
• Carbon-12, which has a natural abundance of 98.89%, and
• Carbon-13, which has a natural abundance of 1.11%.
4.3
To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.
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Slide 12 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
A periodic table is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties.
A periodic table allows you to easily compare the properties of one element (or a group of elements) to another element (or group of elements).
4.3
The Periodic Table—A Preview
Why is a periodic table useful?
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Slide 13 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
The Periodic Table
4.3
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Slide 14 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
• Each horizontal row of the periodic table is called a period.
• Within a given period, the properties of the elements vary as you move across it from element to element.
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Slide 15 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
A Period
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Slide 16 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
• Each vertical column of the periodic table is called a group, or family.
• Elements within a group have similar chemical and physical properties.
4.3
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Slide 17 of 52
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>Distinguishing Among Atoms The Periodic Table—A Preview
A Group or Family (Groups 1-18 regents tables)
4.3
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Slide 18 of 52
Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
4.3 Section Quiz
4.3.
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Slide 19 of 52
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4.3 Section Quiz
1. Isotopes of an element have
a. the same mass number.
b. different atomic numbers.
c. the same number of protons but different numbers of neutrons.
d. the same number of protons but different numbers of electrons.
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Slide 20 of 52
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4.3 Section Quiz
2. How many neutrons are in sulfur-33?
a. 16 neutrons
b. 33 neutrons
c. 17 neutrons
d. 32.06 neutrons