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Chemistry 4.3

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4.3

Distinguishing Among Atoms

Connecting to Your World

Just as apples come in different varieties, a chemical element can come in different “varieties” called isotopes.

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4.3

Distinguishing Among Atoms > Atomic Number

Atomic Number

What makes one element different from another?

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4.3

Distinguishing Among Atoms > Atomic Number Elements are different because they contain different numbers of protons.

The

atomic number

of an element is the number of protons in the nucleus of an atom of that element.

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4.3

Distinguishing Among Atoms > Atomic Number

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Atomic Number

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Practice Problems for Conceptual Problem 4.1

Problem Solving 4.15

Solve Problem 15 with the help of an interactive guided tutorial.

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4.3

Distinguishing Among Atoms > Mass Number

Mass Number

How do you find the number of neutrons in an atom?

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4.3

Distinguishing Among Atoms > Mass Number

The total number of protons and neutrons in an atom is called the

mass number.

The number of neutrons in an atom is the difference between the mass number and atomic number.

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4.3

Distinguishing Among Atoms > Mass Number

Au is the chemical symbol for gold.

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SAMPLE PROBLEM 4.1

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SAMPLE PROBLEM 4.1

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SAMPLE PROBLEM 4.1

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SAMPLE PROBLEM 4.1

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Practice Problems for Sample Problem 4.1

Problem Solving 4.17

Solve Problem 17 with the help of an interactive guided tutorial.

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4.3

Distinguishing Among Atoms > Isotopes

Isotopes

How do isotopes of an element differ?

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4.3

Distinguishing Among Atoms > Isotopes Isotopes

are atoms that have the same number of protons but different numbers of neutrons.

Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

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4.3

Distinguishing Among Atoms > Isotopes

Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons.

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Practice Problems for Conceptual Problem 4.2

Problem Solving 4.20

Solve Problem 20 with the help of an interactive guided tutorial.

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4.3

Distinguishing Among Atoms > Atomic Mass

Atomic Mass

How do you calculate the atomic mass of an element?

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4.3

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.

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4.3

Distinguishing Among Atoms > Atomic Mass Some Elements and Their Isotopes

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4.3

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.

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4.3

Distinguishing Among Atoms > Atomic Mass Weighted Average Mass of a Chlorine Atom

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Practice Problems for Conceptual Problem 4.3

for Conceptual Problem 4.3

Problem Solving 4.21

Solve Problem 21 with the help of an interactive guided tutorial .

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4.3

Distinguishing Among Atoms > Atomic Mass 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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4.3

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%.

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SAMPLE PROBLEM 4.2

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SAMPLE PROBLEM 4.2

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SAMPLE PROBLEM 4.2

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SAMPLE PROBLEM 4.2

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Practice Problems for Sample Problem 4.2

Problem Solving 4.24

Solve Problem 24 with the help of an interactive guided tutorial.

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4.3

Distinguishing Among Atoms > The Periodic Table —A Preview

The Periodic Table —A Preview

Why is a periodic table useful?

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4.3

Distinguishing Among Atoms > The Periodic Table —A Preview

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).

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4.3

Distinguishing Among Atoms > The Periodic Table —A Preview The Periodic Table

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4.3

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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4.3

Distinguishing Among Atoms > The Periodic Table —A Preview A Period

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4.3

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.

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4.3

Distinguishing Among Atoms > The Periodic Table —A Preview A Group or Family

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4.3 Section Quiz Assess students’ understanding of the concepts in Section 4.3.

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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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4.3 Section Quiz

2. How many neutrons are in sulfur-33?

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4.3 Section Quiz

3. If sulfur contained 90.0% sulfur-32 and 10.0% sulfur-34, its atomic mass would be a. 32.2 amu.

b. 32.4 amu.

c. 33.0 amu.

d. 35.4 amu.

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Distinguishing Among Atoms > Concept Map

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Slide 1

Transcript Slide 1

Distinguishing Among Atoms

Atomic Number

Mass Number

Isotopes

Atomic Mass

The Periodic Table —A Preview

END OF SHOW

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