Chapter 5: The Periodic Table

1. Chapter 5: The Periodic Table PEPS Rainier Jr/Sr High School Mr. Taylor

2. Section 1: Organizing the Elements • Russian chemist Dmitri Mendeleev in the 1860’s knew about 60 elements and their atomic masses. • When he placed these elements in order by atomic mass he saw that chemical properties repeated at regular intervals (periodic repetition).

3. Section 1: Organizing the Elements • Mendeleev’s table had gaps in it but he predicted the properties of these “gap” elements • Predictions were close when these elements were discovered.

4. Section 1: Organizing the Elements • A few elements did not fit the pattern • Henry Moseley (English chemist) rearranged the elements by atomic number; problem solved. • The Periodic Law: when arranged by increasing atomic number, elements have similar chemical properties that repeat at regular intervals (periods).

5. Section 1: Organizing the Elements Chemical name Chemical symbol

6. Section 1: Organizing the Elements • The rows are called periods • Elements become less metallic from left to right • The columns are called groups. • Each column (group) has similar chemical properties

7. Section 2: Exploring the Periodic Table • The periodic repetition of chemical properties is the result of the arrangement of electrons in the outer energy level (valence electrons). • Variations in physical properties are due to different atomic numbers (protons).

8. Section 2: Exploring the Periodic Table • Elements are place in; • Rows by the number of electron energy levels • Columns by the number of electrons in the outer energy level (valence electrons).

9. Section 2: Exploring the Periodic Table • Ion Formation • Atoms may gain or lose electrons to form ions • Ions are charged particles because they do not have the same number of protons and electrons (unbalanced charges).

10. Section 2: Exploring the Periodic Table • Ion Formation • Atoms gain or lose electrons to achieve a full outer energy level. • Group 1; loses an electron easily, has a positive charge (cation). • Group 17; gain an electron easily, has a negative charge (anion)

11. Section 2: Exploring the Periodic Table • Metals vs non-metals • Metals are • Shiny solids (mostly) • Malleable (able to be hammered into shapes) • Ductile (can be stretched into wires) • Conductors of electricity and heat

12. Section 2: Exploring the Periodic Table • Metals vs non-metals • Non-metals are • Solids, liquids, or gases at room temp. • Often dull and brittle • Poor conductors of heat and electricity (insulators)

13. Section 2: Exploring the Periodic Table • Metals vs non-metals • Semiconductors • Have some properties of metals and non-metals • Are used in computer chips

14. Section 3: Families of Elements • Elements of a family have the same number of valence electrons • Metals: left side of table • Non-metals: right side of table

15. Section 3: Families of Elements • Alkali metals: Group 1 • One valence electron • Form an ion with a 1+ charge • HIGHLY reactive • Never found in Nature except combined with another element in a compound

16. Section 3: Families of Elements • Alkaline Earth metals: Group 2 • 2 valence electrons • Form a 2+ ion • Very reactive, but less than Group 1

17. Section 3: Families of Elements • Transition Metals • Number of valence electrons varies • Some are reactive (iron), some are not (Gold) • Many metals we use everyday are in this group (Iron, gold, aluminum, copper).

18. Section 3: Families of Elements • Noble gases: Group 18 • Full outer valence electron energy level • Non-reactive gases do not usually form compounds or molecules.

19. Section 3: Families of Elements • Halogens: Group 17 • 7 electrons in outer energy level (almost full). • Gain 1 electron easily to fill the level; 1- charge • VERY reactive; combine easily with metals to form a salt (NaCl, KCl, SnF2).

20. Section 3: Families of Elements • Other non-metals • Oxygen and Nitrogen are the most abundant gases in the atmosphere. • Carbon compounds form the basis of most of the molecules in living organisms.

21. Section 3: Families of Elements • Semiconductors • Also called metalloids • Silicon makes up 28% of the matter in the Earth’s crust • Sand is mostly silicon dioxide.