1. Slide 1 of 35 Chemistry 4.3

2. © Copyright Pearson Prentice Hall Distinguishing Among Atoms > Slide 2 of 35 4.3 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.

3. Slide 3 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Atomic Number 4.3 Atomic Numbers Differ Mass Number is the Sum of the # of Protons and the # of Neutrons

4. © Copyright Pearson Prentice Hall Slide 4 of 35

5. © Copyright Pearson Prentice Hall Slide 5 of 35 Practice Problems for Conceptual Problem 4.1 Problem Solving 4.15 Solve Problem 15 with the help of an interactive guided tutorial.

6. Slide 6 of 35 © Copyright Pearson Prentice Hall > 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. 4.3 Mass number = # of Protons + # of Neutrons

7. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 7 of 35 4.1

8. Slide 8 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms 4.3 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.

9. Slide 9 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Isotopes Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons. 4.3 Symbol Notation for different isotopes of Neon

10. Slide 10 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Symbol Notation You can describe an isotope using symbol notation:

11. Slide 11 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Mass Number Au is the chemical symbol for gold. This is gold’s symbol notation. 4.3

12. © Copyright Pearson Prentice Hall Slide 12 of 35 Practice Problems for Sample Problem 4.1 Problem Solving 4.17 Solve Problem 17 with the help of an interactive guided tutorial.

13. Slide 13 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Hyphen Notation You can also indicate isotopes using hyphen notation: Element’s Name – Mass Number

14. © Copyright Pearson Prentice Hall Slide 14 of 35

15. © Copyright Pearson Prentice Hall Slide 15 of 35 Practice Problems for Conceptual Problem 4.2 Problem Solving 4.20 Solve Problem 20 with the help of an interactive guided tutorial.

16. Slide 16 of 35 © Copyright Pearson Prentice Hall > 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

17. Slide 17 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms Atomic Mass Some Elements and Their Isotopes 4.3

18. © Copyright Pearson Prentice Hall Distinguishing Among Atoms > Slide 18 of 35 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. 4.3

19. Slide 19 of 35 © Copyright Pearson Prentice Hall > 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 Never use % abundance, only relative abundance (i.e. % abundance/100)

20. Slide 20 of 35 © Copyright Pearson Prentice Hall > 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

21. © Copyright Pearson Prentice Hall Slide 21 of 35

22. © Copyright Pearson Prentice Hall Slide 22 of 35 Practice Problems for Conceptual Problem 4.3 Problem Solving 4.21 Solve Problem 21 with the help of an interactive guided tutorial. for Conceptual Problem 4.3

23. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 23 of 35 4.2

24. © Copyright Pearson Prentice Hall Slide 24 of 35 Practice Problems for Sample Problem 4.2 Problem Solving 4.24 Solve Problem 24 with the help of an interactive guided tutorial.

25. Slide 25 of 35 © Copyright Pearson Prentice Hall > 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

26. Slide 26 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms The Periodic Table—A Preview The Periodic Table 4.3

27. Slide 27 of 35 © Copyright Pearson Prentice Hall > 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. 4.3

28. Slide 28 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms The Periodic Table—A Preview A Period 4.3

29. Slide 29 of 35 © Copyright Pearson Prentice Hall > 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

30. Slide 30 of 35 © Copyright Pearson Prentice Hall > Distinguishing Among Atoms The Periodic Table—A Preview A Group or Family 4.3

31. © Copyright Pearson Prentice Hall Slide 31 of 35 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 4.3 Section Quiz 4.3.

32. © Copyright Pearson Prentice Hall Slide 32 of 35 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. 4.3 Section Quiz

33. © Copyright Pearson Prentice Hall Slide 33 of 35 2. How many neutrons are in sulfur-33? a.16 neutrons b.33 neutrons c.17 neutrons d.32.06 neutrons 4.3 Section Quiz

34. © Copyright Pearson Prentice Hall Slide 34 of 35 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. 4.3 Section Quiz

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