1. MATERIALS PART B Periodic Trends

2. History Mendeleev-Russian 1869 organized elements according to mass and properties noticed that properties repeated periodically predicted elements, later identified as Sc,Ga,Ge

3. History Henry Moseley-1911 Used X-rays for determining the # of protons This is how our current periodic table is arranged.

4. Periodic Law Physical and chemical properties repeat periodically if arranged according to atomic number.  “Recurring or reappearing from time to time;” http://www.thefreedictionary.com http://www.thefreedictionary.com Look for patterns

5. History Additional changes since Medeleev  Noble gases- William Ramsay (1906)  Lanthanides/Actinides- Glenn Seaborg (1950)

6. The Electrical Nature of Matter  Protons- positive  mass of 1 atomic mass unit (amu)  in nucleus  Electrons- negative  very small mass  outside of nucleus  Neutrons- neutral (no charge)  mass 1 amu  in nucleus

7. The Electrical Nature of Matter Let’s try  An atom has:  15 protons + 15 electrons =  20 protons + 21 electrons =  19 protons + 18 electrons =  10 protons + 12 electrons=

8. Counting Subatomic Particles Atomic Number  # of protons  Identifies the element - this also equals the # of electrons because atoms are neutral

9. Counting Subatomic Particles Mass Number  # of protons + # of neutrons  Find this by rounding the mass on the periodic table  Examples: See practice sheet

10. Ions and Ionic Compounds Ions:  charged atoms;  atoms that have gained or lost electrons to form negative or positive ions Ionic Compounds: compounds composed of positive and negative ions

11. The Electrical Nature of Matter Opposites attract-  this is the glue to hold atoms together  These are chemical bonds.

12. Ions and Ionic Compounds Cation: a positively charged ion (Na + ) Anion: a negatively charged ion (Cl - ) Polyatomic ion: (many-atoms) an ions made of two or more bonded atoms (NH 4 + or NO 3 - )

13. Ions and Ionic Compounds Step 1: Write the symbols for the ions side by side, with the positive ion (or most metallic element) first Step 2: Cross over the charge values to give subscripts Step 3: Check the subscripts by making sure the total charge of ions in the compound is zero, simplify Step 4: Write the formula

14. Ions and Ionic Compounds Let’s try: Need to use ion chart zinc oxide aluminum sulfide calcium carbonate

15. Ions and Ionic Compounds Naming Compounds  Nomenclature: the method of naming chemical compounds 1. write the name of the element having a positive charge 2. add the name of the negative element 3. the negative element must be modified to end in – ide

16. Ions and Ionic Compounds Let’s try: Use the chart of ions NaI 2 K 2 O BaSO 4