Distinguishing Among Atoms

1. Distinguishing AmongAtoms 4.3 • Just as apples come in different varieties, a chemical element can come in different “varieties” called isotopes.

2. 4.3 Atomic Number • Atomic Number • What makes one element different from another? • 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. 4.3 Atomic Number

5. Atomic Number

7. for Conceptual Problem 4.1

8. 4.3 Mass Number • Mass Number • How do you find the number of neutrons in an atom? • 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.

9. 4.3 Mass Number • How many protons, electrons and neutrons does this isotope of gold have?

10. 4.1

11. 4.1

12. for Sample Problem 4.1 Problem Solving 4.17 Solve Problem 17 with the help of an interactive guided tutorial.

13. 4.3 Isotopes • How do isotopes of an element differ? • 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.

14. 4.3 Isotopes • Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons.

18. for Conceptual Problem 4.2 Problem Solving 4.20 Solve Problem 20 with the help of an interactive guided tutorial.

19. 4.3 Atomic Mass • Atomic Mass • How do you calculate the atomic mass of an element? • 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.

20. 4.3 Atomic Mass • Some Elements and Their Isotopes

21. 4.3 Atomic Mass • Weighted Average Mass of a Chlorine Atom

25. 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.

26. 4.3 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.

27. 4.3 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%.

28. 4.2

29. 4.2

30. 4.2

31. 4.2

32. for Sample Problem 4.2 Problem Solving 4.24 Solve Problem 24 with the help of an interactive guided tutorial.

33. 4.3 The Periodic Table—A Preview • The Periodic Table—A Preview • Why is a periodic table useful?

34. 4.3 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).

35. 4.3 The Periodic Table—A Preview • The Periodic Table

36. 4.3 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.

37. 4.3 The Periodic Table—A Preview • A Period

38. 4.3 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.

39. 4.3 The Periodic Table—A Preview • A Group or Family

40. 4.3 Section Quiz • 4.3.

41. 4.3 Section Quiz • 1. Isotopes of an element have • the same mass number. • different atomic numbers. • the same number of protons but different numbers of neutrons. • the same number of protons but different numbers of electrons.

42. 4.3 Section Quiz • 2. How many neutrons are in sulfur-33? • 16 neutrons • 33 neutrons • 17 neutrons • 32.06 neutrons

43. 4.3 Section Quiz • 3. If sulfur contained 90.0% sulfur-32 and 10.0% sulfur-34, its atomic mass would be • 32.2 amu. • 32.4 amu. • 33.0 amu. • 35.4 amu.