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Chapter 5

Chapter 5. The Periodic Table. 5-1 Organizing the Elements. What does the word “ periodic ” mean? Periodic : recurring at regular intervals Periodic table – is an arrangement of elements in columns based on a set of properties that repeat from row to row. Mendeleev 1869.

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Chapter 5

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  1. Chapter 5 The Periodic Table

  2. 5-1 Organizing the Elements • What does the word “periodic” mean? • Periodic: recurring at regular intervals • Periodic table – is an arrangement of elements in columns based on a set of properties that repeat from row to row

  3. Mendeleev 1869 • See Figure 3 on page 127 • Arranged elements according to increasing atomic mass in rows • Put elements of similar properties in the same column • Left blank spots in table which predicted properties of elements not yet discovered

  4. Evidence Supporting Mendeleev’s Table • Named eka-aluminum to the element that belonged one space below aluminum on the table • 1875- French chemist discovered a new element and named it gallium (Ga) • Gallium is a soft metal used in traffic signals

  5. Similarity of the two • Eka-aluminum and Gallium were similar in properties, so they were determined to be the same • The close match between Mendeleev’s prediction and the actual properties of new elements showed how useful his periodic table could be

  6. Questions • Which of the following is a symbol for an element? • Aluminum • Al • al • AL

  7. Questions 3. What happens to the composition of matter during a physical change? Does it change or remain the same?

  8. Questions 2. Is flammability a physical property or a chemical property?

  9. Questions 4. What does the atomic number of an element represent?

  10. Question 5. Isotopes of element have different numbers of • Neutrons • Electrons • Protons • nuclei

  11. Question 6. True or False : Electrons in atoms occupy orbitals in energy levels

  12. 5-2 The Modern Periodic Table • Mendeleev developed the periodic table before the discovery of protons. • In the modern periodic table, elements are arranged by increasing atomic number

  13. Periods • Each row in the table of elements is called a period • Period 1 has two elements • Periods 2 and 3 have 8 elements • Periods 4 and 5 have 18 elements • Period 6 has 32 elements • There are 7 periods total on the periodic table • The number of electrons per period varies because of the number of available orbitals increases from energy level to energy level

  14. Groups • Each column on the periodic table is called a group • The elements within a group have similar properties • Properties of elements repeat in a predicable way when atomic number are used to arrange elements into groups • The pattern of repeating properties is the periodic law • There are 18 groups on the periodic table

  15. Atomic Mass • Atomic mass is a value that depends on the distribution of an element’s isotopes in nature and the masses of those isotopes • An atomic mass unit (amu) is defined as one twelfth the mass of carbon-12 atom

  16. Average Atomic Mass • Weighted average of the atomic masses of the naturally occurring isotopes of an element

  17. What is the aver. atomic mass of the chlorine?

  18. Weighted Averages • Average Atomic Mass = • (isotope mass)(relative abundance[dec]) + (isotope mass)(relative abundance[dec]) • (0.75771)(34.96885amu) + (0.24229)(36.96590amu) • = 35.453 amu

  19. ISOTOPES • Atoms of the same element that differ in mass • Have the same # protons but different # neutrons

  20. Classes of Elements • Elements are classified as metals, nonmetals, and metalloids • Metal: • Good conductor of heat & electricity • Ductile –able to be drawn into a fine wire • Malleability – can be hammered or rolled into thin sheets • Nonmetal • Poor conductor of heat & electricity • Brittle • Metalloids • Some characteristics of metals & nonmetals

  21. Beaker Breaker • Isotopes have the same # of _______ but different #of __________ • What is the name of group 1 on the periodic table? • How many periods are there on the periodic table?

  22. Transition Metals • Transition metals are elements that form a bridge between the elements on the left and right sides of the table

  23. The Lanthanides • The 14 elements with atomic numbers from 58(cerium, Ce) to 71(lutetium, Lr) • Similar in chemical and physical properties

  24. The Actinides • The 14 elements with atomic number from 90(thorium, Th) to 103(lawrencium, Lr)

  25. Variation across a period • Across a period from left to right, the elements become less metallic and more nonmetallic in their properties • Most reactive metals are on the left side of the table • Most reactive nonmetals are on the right in Group 17

  26. 5-3 Representative Groups • Valence electron – is an electron that is in the highest occupied energy level of an atom • Elements in a group have similar properties because they have the same number of valence electrons • Valence electrons explain the location of hydrogen, hydrogen has a single electron

  27. Alkali Metals • Elements in Group 1A are called alkali metals. • Single valence electron and are extremely reactive • The reactivity of alkali metals increases from the top of Group 1A to the bottom

  28. The Alkaline Earth Metals • The elements in Group 2A are called alkaline earth metals • All alkaline earth metals have two valence electrons • They are harder than group 1A • Differences in reactivity among the alkaline earth metals are shown by the ways they react with water • Calcium, strontium and barium react easily with cold water • Magnesium will react with hot water. No change appears to occur when beryllium is added to water

  29. The Boron Family • Group 3A contains the metalloid boron. • Aluminum is the most abundant metal in the Earth’s crust • Glass that contains boron is used to make laboratory glassware such as flasks

  30. The Carbon Family • Group 4A contains nonmetal carbon • Two metalloids – silicon and germanium • Two metals – lead and tin • Except for water, most of the compounds in your body contains carbon • Silicon is the second most abundant element in the Earth’s crust

  31. The Nitrogen Family • Group 5A contains two nonmetals – nitrogen and phosphorus • Two metalloids – arsenic and antimony • One metal –bismuth • Besides nitrogen, fertilizers often contain phosphorus

  32. The Oxygen Family • Group 6A has three nonmetals – oxygen, sulfur, and selenium • Two metalloids – tellurium and polonium • All have 6 valence electrons • Oxygen is the most abundant element in the Earth’s crust

  33. The Halogens • The elements in Group 7A are called halogens • They have seven valence electrons • Despite their physical differences, the halogens have similar chemical properties • They are highly reactive nonmetals • Fluorine is the most reactive

  34. The Noble Gases • The elements in Group 8A are called the noble gases • Helium has 2 valence electrons • All other noble gases have 8 valence electrons • The noble gases are colorless and odorless and extremely unreactive • All the noble gases except radon are used in “neon” lights

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