The History and Arrangement of the Periodic Table

1. The History and Arrangement of the Periodic Table

2. History of the Periodic Table • 1869 – Dmitri Mendeleev (Russian Chemist) thought elements may have something in common. • Organized the elements into a table • Made each element a card and listed its properties known at the time (mass, density, color, melting point and valence number).

3. Dmitri Mendeleev (cont.) • Mendeleev organized each card (element) according to its atomic mass (mass #) • Noticed a repeating pattern of valence numbers (1,2,3,4,5 etc..) • Noticed elements fell in to columns (groups) • Noticed all elements in a column had the same valence number and showed similar physical and chemical properties.

4. Henry Moseley • Mendeleev left blank spaces in his table so elements would line up – he also predicted what properties the undiscovered elements would have. • 1913 – Henry Moseley (English Scientist) changed the arrangement of the periodic table. Instead of by increasing atomic mass (mass #), it was arranged by increasing: atomicnumber (# of protons).

5. Arrangement of the Periodic Table • Systematic arrangement of the elements • Arranged by atomic number and properties • Numbered groups / families are in vertical columns • Periods are by amount of energy levels in horizontal rows (1-7) • Divided into metals, nonmetals and metalloids

6. Metals - properties • Elements that begin at the left side of the periodic table • Good conductors of electricity • Shiny • Ductile – can be drawn into thin wires • Malleable – can be hammered into thin sheets and other shapes • High melting point • Tend to loose electrons

7. Nonmetals - properties • Elements that are to the right of the zigzag on the periodic table • Not shiny, dull in appearance • Do not conduct heat or electricity • Are brittle and break easily • Cannot be drawn into wire or hammered into sheets • Lower densities • Lower melting points • Tend to gain electrons

8. Metalloids - properties • Elements that are found along both sides of the zigzag line • Solids • Can be shiny or dull conduct heat and electricity better than nonmetals but not as well as metals • Both ductile and malleable

9. Chemical Groups (Families) • Elements that are in the same group or family (column) of the Periodic Table have similar properties because they have the same number of valence electrons

10. Group (Family) 1 - Alkali Metals • 1 valence electron in outer energy level • Very reactive substances so it easily bonds with other substances • Easily loses 1 electron to form a stable +1 ion (ionic bond) • Never found alone in nature • Soft, silver-white, shiny

11. Group (Family) 2 - Alkaline Earth Metals • 2 valence electrons in outer energy level • Loses 2 electrons to form +2 ions • Second most reactive elements but not as reactive as group #1, so bonds easily with other substances • Never found alone in nature • Will always bond ionically in nature • Found combined with oxygen and other non-metals in the Earth’ crust

12. Groups 3-12 The Transition Metals • 1 or 2 valence electrons • Can lose and or share valence electrons • Can have many multiple electrons in 2nd to last energy levels • Common metals – gold, silver & copper • The U.S. imports at least 60 of these types of elements which are strategic and vital for our economy

13. From Metals to Nonmetals(outer energy level) • Group 13 – Boron Group/Family 3 valence electrons - metalloids and metals in group - usually bonds covalently • Group 14 Carbon Group 4 valence electrons - non-metals, metals and metalloids - will always bond covalently ( electron sharing) - contain elements which are essential for cell functions

14. Group 15 Nitrogen Group 5 valence electrons - non-metals, metalloids and metals - will always bond covalently • Group 16 Oxygen Group 6 valence electrons - non-metals, metalloids and metals - will bond covalently and ionically in nature • Group 17 Halogen Group 7 valence electrons - all non-metals that are very reactive and form compounds called halides ( salts) - bonds covalently and ionically

15. Group 18 Noble Gases 8 valence electrons - colorless - non-reactive ( inert ) / very stable - have a full outer shell filled with electrons - non-metals

16. Rare Earth Elements(Inner Transition Metals) • First Row – Lanthanide Series - naturally found rare Earth metals - all but one is non-radioactive • Second Row – Actinide Series - most are man-made and radioactive - many are short-lived