History of the Periodic Table

1. History of the Periodic Table 1790s Antoine Lavoisier compiled a list of the 23 known elements 1864 John Newlands named the periodic relationship that he observed in chemical properties the “Law of the Octaves”

2. 1869 Demetri Mendeleev • Demonstrated a connection between atomic mass and elemental properties. • Organized the first Periodic Table of the Elements • Predicted the existence and properties of undiscovered elements • Arranged his Periodic Table according to increasing ATOMIC MASSES of the elements

3. In 1870 there were about 70 known elements

4. In 1911 Henry Moseley • Discovered that atoms of each element contain a unique number of protons in their nucleus • Arranged the elements in increasing ATOMIC NUMBER rather than atomic masses as Mendeleev had done

5. Periodicity- A repeating pattern • Periodic Law- States that the chemical and physical properties of elements are periodic functions of their atomic number • Periodic Table- A chart organizing elements by their INCREASING atomic number.

6. FAMILIES YOU MUST KNOW • Family # 1- Alkali Metals Family, Lithium – Francium (Li-Fr) excluding Hydrogen because it is NOT a metal. Hydrogen is a gas! Family #2- Alkaline Earth Metals, (Be – Ra)

7. Family # 17- The Halogens Fluorine – Astatine (F– At) • Family # 18- The Noble Gases Helium – Radon • Transition Metals – Families 3 – 12 the “d” block

8. Periods 6 and 7 • Lanthanides “Rare Earth Metals”, used in TV Period 6 Elements # 58 –71 Very Colorful ------------------------------------------------------------------ • Actinides Radioactive elements 90 --103 Period 7 Most are synthetic or man-made

9. Representative Elements • Elements within the “s” and the “p” blocks