1. Where it all is

2. The Begining  Law of Triads: In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties. In 1829, after discovering the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium he proposed that nature contained triads of elements the middle element had properties that were an average of the other two members when ordered by the atomic weight.

3.  John Newlands determined a repeating pattern of every 8 elements. He called it the law of octaves.  Developed in the 1860’s  Dmitri Mendeleev arranged the first on based on Atomic Masses.  Henry Moseley Arranged the Modern Periodic Table based on Atomic Number.

4.  There has been some disagreement about who deserves credit for being the "father" of the periodic table: ◦ the German Lothar Meyer ◦ or the Russian Dmitri Mendeleev.  Both chemists produced remarkably similar results at the same time working independently of one another. Meyer's 1864 textbook included a rather abbreviated version of a periodic table used to classify the elements.  Unfortunately for Meyer, Mendeleev's table became available to the scientific community via publication (1869) before Meyer's appeared (1870).

5. Mendeleev’s table as published in 1869, with many gaps and uncertainties

6.  Based on increasing atomic number and on electron configurations ◦ Results in repeating chemical and physical properties.  Groups or Families ◦ Columns that go up and down. ◦ There are 18 Groups  Periods ◦ Rows that go across ◦ There are 7 Periods

7. Metals ◦ On the left side ◦ Make up ¾ of all elements ◦ Malleable, Ductile, Conduct electricity, form positive ions.  NonMetals ◦ On the Right side ◦ Dull, Brittle, Insulators, form negative ions  Metalloids (Semimetals) ◦ Found along the staircase between metals and nonmetals, have properties of both.

8.  Highly reactive  Replace Hydrogen in Water  All have 1 valence electron  All are s 1  Forms +1 ions

9.  Very reactive  Don’t replace Hydrogen in Water ◦ Readily burn in O 2 when exposed to heat  Calcium makes up your bones.  Batteries get their name from this group  Have 2 Valence electrons ◦ All are s 2 – forms +2 ions

10.  These are the common metals  All have d orbitals filling  Less reactive then other metals  Copper, Silver, and Gold least reactive  Forms various positive ions

11.  Have 3 Valence electrons ◦ All are s 2 p 1 ◦ All form +3 ions except  Boron which forms a –3 ion  One is a metalloid (Boron)  The rest are all metals

12.  Carbon family has 4 valence electrons  All are s2 p2  Composed of: ◦ one non-metal (Carbon) ◦ Two metaloids (Silicon and Germanium ◦ Two metals (Tin and Lead)

13.  Carbon always forms 4 bonds ◦ All known life based on Carbon  Computers function based on Silicon and Germanium’s unique properties ◦ They conduct electricity but not heat  Lead and Tin are common metals ◦ Used to be used a lot in food storage

14.  All have 5 valence electrons ◦ All are s2 p3  Composed of: ◦ two nonmetals - Nitrogen and Phosphorous ◦ Two metalloids – Arsenic and Antimony ◦ One metal - Bismuth

15.  Nitrogen: ◦ makes up most of the atmosphere ◦ Critical to plant and animal life ◦ Forms strong bonds that are used in explosives  Phosphorous ◦ Critical to plant and animal life

16.  All have 6 valence electrons ◦ All are s2 p4 ◦ Usually form 2 bonds  Form – 2 ions (except Polonium +2, +4 ions)  Composed of: ◦ 3 nonmetals – Oxygen, Sulfur, Selenium ◦ 1 metalloid – Tellerium ◦ 1 metal - Polonium

17.  All have 7 valence electrons ◦ All are s2 p5 ◦ Forms 1 bond  Forms – 1 ions  All are nonmetals  Highly reactive ◦ Never found in nature as single atoms ◦ When pure will form F 2, Cl 2, Br 2, I 2

18.  All have 8 valence electrons ◦ All are s2 p6 ◦ Rarely form bonds  Never form ions ◦ Helium, Neon, Argon have never been found in a compound ◦ Krypton, Xenon, Radium can sometimes be forced to form compounds – but these are very unstable

19.  Called Rare Earths ◦ They are rare on earth - Most are manmade  All are radioactive  All elements greater then Uranium (92) are manmade  Some are used in medical research

20.  Atomic Radius – The size of the atom. ◦ Hard to measure due to cloud not being distinct ◦ Smaller Up and Right ◦ Negative Ions Larger ◦ Positive Ions Smaller  Ionization Energy – The energy required to remove one electron, the more electrons removed, the more energy required. ◦ Greater Up and Right ◦ Fluorine the highest ◦ Francium the lowest

21.  Electronegativity – The ability of atoms to attract electrons during bonding ◦ Greater Up and Right ◦ Fluorine the Greatest Electronegivity ◦ Francium the Lowest  Octet Rule – Atoms Tend to gain, lose or share electrons to have a full (s2, p6) valence shell.  Shielding Effect – The ability of inner electrons to shield valence electrons from the nucleus. Increase Down, Across Same