Unit 5 The Structure of Matter

1. Unit 5 The Structure of Matter Chapter 17 The Elements and The Periodic Table

2. 17B – The Periodic Table • Objectives: • Summarize the early attempts to organize the elements • Describe the organization and feature of Mendeleev’s periodic table • Identify the problems with Mendeleev’s periodic table and how they were solved • State the modern periodic law of the elements • Assignments: Element Stories, Worksheet, and Section Review page 421

3. Organizing the Elements • How would you like to memorize all the physical and chemical properties of every element? • After many attempts to organize the elements Mendeleev finally succeeded • The periodic table of the elements is one of the most useful tools of science • Knowing how it was developed will help you to see how it enables scientists (and students) to remember the chemical properties of elements

4. The Discovery of Periodicity • Johann Dobereiner • Found elements that had similarities and formed triads • De Chancourtois • The first scientist to test the theory of periodicity • Graphed the known elements in order of increasing atomic mass on paper • Rolled into a cylinder so that sixteen mass units marked off its circumference, every eighth element often had similar physical and chemical properties to the elements above and below it • John Newlands • Organized elements in order of increasing atomic masses and displayed them in seven columns • Every eighth element had similar properties • Called these repeating patterns octaves • Called his system the law of octaves • Worked better than Dobereiner’s, but most scientists were still unsatisfied • He was actually ridiculed for comparing a physical property of matter to a musical concept

5. Mendeleev and His Periodic Law • 3 years after Newlands • Arranged the elements in similar style according to increasing atomic mass • Did not believe that all elements repeated after every eight elements • Put elements together according to similar properties and left blank spaces when an element didn’t “fit” • Mendeleev called this principle that the properties of elements vary in a periodic or recurring pattern with their atomic masses the periodic law

6. Revising the Periodic Table • Mendeleev’s table had some problems • Iodine and Tellurium • Nickel and Cobalt • Henry Moseley • The properties of the elements vary with their atomic numbers in a periodic way • Facet • Page 420

7. 17C – Classes of Elements • Objectives: • Describe the properties of metals and nonmetals • Explain how electron configuration affects the properties of metals and nonmetals • Compare metalloids with metals and nonmetals • Define a family or group of elements • Name the major element families and state how many valence electrons a neutral atom of each element has • Define a chemical period and state the significance of the period number • Assignments: Color Code the Periodic Table, Worksheet, and Section Review page 430

8. Classes of Elements

9. Metals • Almost three fourths of the elements are metals • Common Characteristics of Metals • Clean surfaces of most metals have a silvery or metallic luster • All metals except mercury (Hg) are solids at room temperature • Most metals are malleable, or can be rolled or hammered into a shape • Most metals are ductile, or can be drawn into wire • Most metals are good conductors of electricity and heat • Metals tend to be reactive, easily forming bonds

10. Nonmetals • Common Characteristics of Nonmetals • Nonmetals exist as solids, liquids, and gases at room temperature; most are gases • Solid nonmetals exist as brittle crystals that shatter easily • Nonmetals are poor conductors of electricity and heat • Nonmetals have a variety of colors • Six nonmetals called the noble or inert gases do not readily react with other elements • Nonmetals other than the noble gases generally form bonds by sharing or taking electrons from other atoms

11. Metalloids • Also called semimetals • Straddle the stairstep line on the periodic table • Slightly conductive • Manufactured into semiconductors • Computers, portable music players, calculators, cell phones, or a host of other items using digital technology

12. Element Families • Each column on the periodic table is called a family or group • Have the same amount of valence electrons • Same properties • Numbered with 1A, 2A, etc in the US • Also numbered 1-18 for countries other than the US • This designation is preferred by the International Union of Pure and Applied Chemistry (IUPAC) • Be familiar with both!

13. Alkali Metals • Group 1A • 1 valence electron • Very reactive metals • Will combine with oxygen in the air so they need to be stored in a container of oil

14. Alkaline Earth Metals • Group 2A • 2 valence electrons • Slightly less reactive than alkali metals, but not stable enough to remain free in nature • Found in many common minerals

15. Transition Metals • Groups 1B-8B (3-12) • One or two valence electrons • Normally combined in alloys • Inner Transition Metals • Two rows below the periodic table

16. Miscellaneous Families • Boron Family • Group 3A • 3 valence electrons • Carbon Family • Group 4A • 4 valence electrons • Nitrogen Family • Group 5A • 5 valence electrons • Oxygen Family • Group 6A • 6 valence electrons

17. Halogens • Group 7A • 7 valence electrons • Very reactive • Exist as diatomic molecules • As atomic number increases the color darkens

18. Noble Gases • Group 8A • Also called Inert Gases • Very stable and nonreactive due to a full valence shell

19. Elemental Periods • Horizontal rows in the periodic table are called periods or series • Elements in the same period do not have similar properties • Numbered on the side of the table and tells you how many energy levels are in the atom • Facet • Page 429

20. 17D – Periodic Trends • Objectives: • Explain how the electron structure of an atom determines its properties • Draw an electron dot structure for a given atom • Explain how conductivity and atomic size generally vary with atomic number from left to right and top to bottom on the periodic table • Assignments: Element Stories, Worksheet, and Section Review page 432

21. Electron Structure & The Periodic Table • The number of valence electrons is important in determining the chemical and many physical properties of an element • Properties change with the increase of atomic number, and those changes reveal predictable trends across periods and within families • Electron dot notation • Illustrates the arrangement of valence electrons in an atom • Dots represent valence electrons • Elements group number determines how many dots surround its symbol

22. Electron Structure & The Periodic Table

23. Periodic Trends • Element properties repeat in a periodic way • Atomic Size • Increases down a family and decreases across a period • More trends discussed later: • Electronegativity • Electron affinity • Ionic size • Ionization energy