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Periodic Trends

Periodic Trends. Materials Part B. History. Mendeleev -Russian 1869 organized elements according to mass and properties noticed that properties repeated periodically predicted elements, later identified as Sc,Ga,Ge. History. Henry Moseley -1911

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Periodic Trends

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  1. Periodic Trends Materials Part B

  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 • 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 (NH4+ or NO3-)

  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 NaI2 K2O BaSO4

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