2. Atoms, Elements, and Compounds

3. Chapter 7: Elements and the Periodic Table 7.1 The Periodic Table 7.2 Properties of the Elements

4. Investigation 7A What is the periodic table and how many elements are there? The Periodic Table

5. 7.1 Physical properties Characteristics that you can see through direct observation are called physical properties. Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas). Melting point, boiling point, and specific heat are also physical properties.

6. 7.1 Chemical properties Properties that can only be observed when one substance changes into a different substance are called chemical properties. Any change that transforms one substance into a different substance is called a chemical change.

7. 7.1 The Periodic Table The periodic table organizes the elements according to how they combine with other elements (chemical properties). The periodic table is organized in order of increasing atomic number.

8. 7.1 The Periodic Table The periodic table is further divided into periods and groups. Each horizontal row is called a period. Each vertical column is called a group.

9. Metals and Nonmetals Metals: shiny, opaque A good conductor of heat and electricity Ductile Left side of the zig- zag line Nonmetals: Poor conductors Brittle as solids Dull To the right of zig- zag line except hydrogen

10. Atomic Mass The average mass of all known isotopes of an element, expressed in AMU Example: Li atomic number of 3, has an atomic mass of 6.941 Example: B atomic number of 5, has an atomic mass of 10.811

12. Groups of the Periodic Table Alkali Metals: (group #1) Includes elements Li, Na, K, Rb, Cs Soft, silvery metals that are highly reactive. Each combine in a two to one ratio with oxygen Have one Valence electron

13. Alkaline Earth Metals (group #2) metals: Include elements Be, Mg, Ca, Sr, Ba These are less reactive than the group 1 elements Form oxides with oxygen in a ratio of 1 to 1. Have two valence electrons

14. Halogens Group 17 elements Nonmetals Toxic gases or liquids Include elements F, Cl, Br, I Form salts with alkali metals 7 valence electrons

15. Noble Gases Group 18 Include elements He, ne, Ar Kr, Xe Are completely inert, un-reactive in nature All gases Full shell of 8 electrons

16. Transition Metals Groups 3-12 Middle of the table Include Ti, Fe, Cu Good conductors Have either 1 or 2 valence electrons Considered reactive, but less than groups 1 and 2

18. 7.1 Energy levels and the periodic table The periods (rows) of the periodic table correspond to the energy levels in the atom.

19. 7.1 Energy levels and the periodic table