1. Unit 2: Periodicity & the Periodic Table

2. I. History A.Dmitri Mendeleev – first person to organize elements based on atomic mass left gaps for elements not discovered yet B. Due to isotopes and other information, the modern table is arranged by order of increasing atomic number

3. II. Types of Elements A. Metals – left of stair step line 85% of elements tend to lose electrons shiny (lustrous) – but can tarnish if react with oxygen ductile – shaped into a wire malleable – hammered into sheets good conductors of heat & electricity

4. B. Non-metals – right of stair step line (except Hydrogen) tend to gain electrons brittle poor conductors of heat & electricity can be solid or gas, only 1 liquid

5. C. Metalloids – 7 elements around stair step line B, Si, Ge, As, Sb, Te & Po (At excluded due to radioactivity) exhibit properties of both metals & non-metals

6. III. Regions of Table groups (families) – columns (1-18) periods – rows (1-7) A. Main Group (Representative) Elements- Groups of elements in the “s” & “p” blocks of the table

7. Hydrogen- doesn’t belong to any group found above group 1, although it is not a metal chemically behaves more like group 1 elements

8. Groups with special names 1. Alkali metals - group 1 - most reactive metals - video - 1 valence electron (ns 1 ) 2. Alkaline Earth Metals – group 2 - less reactive than group 1 - 2 valence electrons (ns 2 ) 3. Chalcogens – group 16 (or 6A) - 6 valence electrons (ns 2 p 4 ) 4. Halogens – group 17 (or 7A) - most reactive non-metals - 7 valence electrons (ns 2 p 5 ) 5. Noble Gases - group 18 (8A) - non-reactive non-metals - 8 valence electrons (ns 2 p 6 ) *except He = 2 valence electrons

9. B. Transition Metals – metals in the “d” block of table have 1 or 2 valence electrons in “s” orbital range in reactivity

10. C. Inner Transition Metals- in “f” block of table referred to as series Lanthanide Series –  first row of “f” block  all are metals Actinide Series –  second row of “f” block  most are radioactive & man-made (synthetic)