2. Chapter 5 The Periodic Table

3. 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

4. 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

5. 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

6. 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

7. Questions 1.Which of the following is a symbol for an element? a.Aluminum b.Al c.al d.AL

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

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

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

11. Question 5. Isotopes of element have different numbers of a.Neutrons b.Electrons c.Protons d.nuclei

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

13. 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

14. 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

15. 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

16. 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

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

18. What is the aver. atomic mass of the chlorine? IsotopeIsotope Mass (amu) % Abundance Chlorine-3534.9688575.771 Chlorine-3736.9659024.229

19. 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

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

21. 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

22. Beaker Breaker 1.Isotopes have the same # of _______ but different #of __________ 2.What is the name of group 1 on the periodic table? 3.How many periods are there on the periodic table?

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

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

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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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