Chapter 12: ATOMS AND THE PERIODIC TABLE

1. Chapter 12: ATOMS AND THE PERIODIC TABLE

2. This lecture will help you understand: • Atoms Are Ancient and Empty • The Elements • Protons and Neutrons • The Periodic Table • Periods and Groups • Physical and Conceptual Models • Identifying Atoms Using the Spectroscope • The Quantum Hypothesis • Electron Waves • The Shell Model

3. Atoms Are Ancient and Empty Atoms are • ancient • origin of most atoms goes back to birth of universe • mostly empty space Elements heavier than hydrogen and much of the helium were produced in the interiors of stars.

4. Atomic Nucleus

6. Atoms Are Ancient and Empty CHECK YOUR NEIGHBOR Which of the following are incorrect statements about the atom? A. Atoms have been around since the beginning of the universe. • Atoms are mostly empty space. • Atoms are perpetually moving. • Atoms are manufactured in plants, and in humans during pregnancy.

7. Atoms Are Ancient and Empty CHECK YOUR ANSWER Which of the following are incorrect statements about the atom? A. Atoms have been around since the beginning of the universe. • Atoms are mostly empty space. • Atoms are perpetually moving. • Atoms are manufactured in plants, and in humans during pregnancy.

8. The Elements • Element: A material made of only one kind of atom. Pure gold is an example as it is made of only gold atoms.

9. The Elements • Element: A material made of only one kind of atom. Pure gold is an example as it is made of only gold atoms. • Atom: The fundamental unit of an element.

10. The Elements • Element: A material made of only one kind of atom. Pure gold is an example as it is made of only gold atoms. • Atom: The fundamental unit of an element. The term “element” is used when referring to macroscopic quantities. The term “atom” is used when discussing the submicroscopic.

11. The Elements Atoms: • make up all matter around us • to date, 115 distinct kinds of atoms— 90 found in nature, remainder synthesized Element any material consisting of only one type of atom

12. Protons and Neutrons Protons: • carry a positive charge—same quantity of charge as electrons • are about 1800 times as massive as an electron • have the same number of protons in the nucleus as electrons surrounding the nucleus of an electrically neutral atom

13. Protons and Neutrons Electrons: • are identical • repel electrons of neighboring atoms • have electrical repulsion that prevents atomic closeness

14. Protons and Neutrons Atomic number: is the number of protons in each element listed in the periodic table. Neutrons: • accompany protons in the nucleus • have about the same mass as protons but no charge, so are electrically neutral Both protons and neutrons are nucleons.

15. Isotopes and Atomic Mass Isotopes: • refers to atoms of the same element that contain the same number of protons but different numbers of neutrons in the nucleus • identified by mass number, which is the total number of protons and neutrons in the nucleus • differ only in mass and not by electric charge; therefore, isotopes share many characteristics Total number of neutrons in isotope = mass number – atomic number

16. Isotopes and Atomic Mass Atomic mass: • total mass of the atom(s) [protons, neutrons, and electrons] • listed in periodic table as atomic mass unit One atomic mass unit is equal to 1.661  10–24 gram or 1.661  10–27 kg

17. Isotopes and Atomic Mass CHECK YOUR NEIGHBOR The atomic number of an element matches the number of A. protons in the nucleus of an atom. • electrons in a neutral atom. • both of the above. • none of the above.

18. Isotopes and Atomic Mass CHECK YOUR ANSWER The atomic number of an element matches the number of A. protons in the nucleus of an atom. • electrons in a neutral atom. • both of the above. • none of the above. Comment: When the atomic number doesn’t match the number of electrons, the atom is an ion.

19. Isotopes and Atomic Mass CHECK YOUR NEIGHBOR A nucleus with an atomic number of 44 and a mass number of 100 must have A. 44 neutrons. • 56 neutrons. • 100 neutrons. • none of the above.

20. Isotopes and Atomic Mass CHECK YOUR ANSWER A nucleus with an atomic number of 44 and a mass number of 100 must have A. 44 neutrons. • 56 neutrons. • 100 neutrons. • none of the above. Comment: Be sure to distinguish between neutron and nucleon. Of the 100 nucleons in the nucleus, 56 are neutrons. A neutron is a nucleon, as is a proton.

21. The Periodic Table • The Periodic Table is a listing of all the known elements.

22. The Periodic Table • The Periodic Table is a listing of all the known elements. • It is NOT something to be memorized.

23. The Periodic Table • The Periodic Table is a listing of all the known elements. • It is NOT something to be memorized. • Instead, we learn how to READ the Periodic Table.

24. The Periodic Table • The Periodic Table is a listing of all the known elements. • It is NOT something to be memorized. • Instead, we learn how to READ the Periodic Table. • A chemist uses the Periodic Table much like a writer uses a dictionary. NEITHER need be memorized!

26. The Periodic Table • The elements are highly organized within the Periodic Table.

27. The Periodic Table • The elements are highly organized within the Periodic Table. • Each vertical column is called a “group.”

28. The Periodic Table • The elements are highly organized within the Periodic Table. • Each vertical column is called a “group.” • Each horizontal row is called a “period.”

29. The Periodic Table

30. The Periodic Table

31. The Periodic Table

32. The Periodic Table

33. The Periodic Table CHECK YOUR NEIGHBOR Which is larger: a lithium atom or a fluorine atom? Li F A. A lithium atom B. A fluorine atom C. There is no way to tell without memorizing the periodic table.

34. The Periodic Table CHECK YOUR ANSWER Which is larger: a lithium atom or a fluorine atom? Li F A. A lithium atom B. A fluorine atom C. There is no way to tell without memorizing the periodic table.

35. The Periodic Table CHECK YOUR NEIGHBOR Which is larger: an arsenic atom or a sulfur atom? S As A. An arsenic atom B. A sulfur atom C. There is no way to tell without memorizing the periodic table.

36. The Periodic Table CHECK YOUR ANSWER Which is larger: an arsenic atom or a sulfur atom? S As A. An arsenic atom B. A sulfur atom C. There is no way to tell without memorizing the periodic table.

37. Physical and Conceptual Models • Physical model replicates the object at a convenient scale

38. Physical and Conceptual Models • Physical model replicates the object at a convenient scale • Conceptual model describes a system

39. Physical and Conceptual Models • Physical model replicates the object at a convenient scale • Conceptual model describes a system -An atom is best described by a conceptual model.

40. Identifying Atoms Using the Spectroscope Spectroscope: • an instrument that separates and spreads light into its component frequencies • allows analysis of light emitted by elements when they are made to glow—identifies each element by its characteristic pattern Each element emits a distinctive glow when energized and displays a distinctive spectrum.

41. Identifying Atoms Using the Spectroscope Atomic spectrum is an element’s fingerprint—a pattern of discrete (distinct) frequencies of light. Discoveries of atomic spectrum of hydrogen: • A researcher in the 1800s noted that hydrogen has a more orderly atomic spectrum than others. • Johann Balmer expressed line positions by a mathematical formula. • Johannes Rydberg noted that the sum of the frequencies of two lines often equals the frequency of a third line.

42. Identifying Atoms Using the Spectroscope Spectral Lines of Various Elements

43. Identifying Atoms Using the Spectroscope Atomic Excitation

44. Identifying Atoms Using the Spectroscope Three transitions in an atom. The sum of the energies (and frequencies) for jumps A and B equals the energy (and frequency) of jump C.

45. Identifying Atoms Using the Spectroscope CHECK YOUR NEIGHBOR Each spectral line in an atomic spectrum represents A. a specific frequency of light emitted by an element. • one of the many colors of an element. • a pattern characteristic of the element. • all of the above.

46. Identifying Atoms Using the Spectroscope CHECK YOUR NEIGHBOR Each spectral line in an atomic spectrum represents A. a specific frequency of light emitted by an element. • one of the many colors of an element. • a pattern characteristic of the element. • all of the above. Explanation: Many lines make up a pattern that is characteristic of the element, so choice C doesn’t fly. Interestingly, the line shape of each spectral line is an image of a thin slit in the spectroscope.

47. Identifying Atoms Using the Spectroscope CHECK YOUR NEIGHBOR The hydrogen spectrum consists of many spectral lines. How can this simple element have so many lines? A. One electron can be boosted to many different energy levels. • The electron can move at a variety of speeds. • The electron can vibrate at a variety of frequencies. • Many standing electron waves can fit in the shell of the hydrogen atom.

48. Identifying Atoms Using the Spectroscope CHECK YOUR NEIGHBOR The hydrogen spectrum consists of many spectral lines. How can this simple element have so many lines? A. One electron can be boosted to many different energy levels. • The electron can move at a variety of speeds. • The electron can vibrate at a variety of frequencies. • Many standing electron waves can fit in the shell of the hydrogen atom.

49. Identifying Atoms Using the Spectroscope CHECK YOUR NEIGHBOR When an atom is excited, its A. electrons are boosted to higher energy levels. • atoms are charged with light energy. • atoms are made to shake, rattle, and roll. • none of the above.

50. Identifying Atoms Using the Spectroscope CHECK YOUR ANSWER When an atom is excited, its A. electrons are boosted to higher energy levels. • atoms are charged with light energy. • atoms are made to shake, rattle, and roll. • none of the above.