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The History and Arrangement of the Periodic Table

The History and Arrangement of the Periodic Table. History of the Periodic Table. 1869 – Dmitri Mendeleev (Russian Chemist) thought elements may have something in common. Organized the elements into a table

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The History and Arrangement of the Periodic Table

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  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 • Noticed a repeating pattern of valence numbers (1, 2, 3, 4, 5, etc.) • Noticed elements fell into columns (groups or families) • Noticed all elements in a column had the same valence number and showed similar physical and chemical properties.

  4. Dmitri Mendeleev (cont.) • Mendeleev left blank spaces in his table so elements would line up – he also predicted what properties the undiscovered elements would have. • He predicted properties of five of these elements and their compounds. Three of these missing elements were discovered by others within 15 years. • The element, atomic number 101, has been named after Mendeleev.

  5. Henry Moseley • 1913 – Henry Moseley (English Scientist) changed the arrangement of the periodic table. • Instead of by increasing atomic mass, it was arranged by increasing atomic number (# of protons).

  6. 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 regions: metals, nonmetals and metalloids

  7. Metals - properties • Elements on the left side of the 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 lose electrons

  8. Nonmetals - properties • Elements to the right of the zigzag on the table • Do not conduct heat or electricity • Dull in appearance (not shiny) • Brittle or break easily • Not ductile or malleable (cannot be drawn into wire or hammered into sheets) • Lower densities • Lower melting points • Tend to gain electrons

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

  10. 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

  11. Group (Family) 1 - Alkali Metals • 1 valence electron in outer energy level • Very reactive, bond easily with other substances (unstable and explosive) • Never found alone in nature • Soft, silver-white, shiny • Easily lose 1 electron to form a stable +1 ion • Form ionic bonds Note: • Hydrogen is a nonmetal gas, and forms covalent bonds. So why is it in this Alkali Metal family?

  12. Hydrogen is a nonmetal gas and forms covalent bonds. So why is it in the Alkali Metal family? The number of valence electrons = 1

  13. Group/Family 2 - Alkaline Earth Metals • 2 valence electrons in outer energy level • 2nd most reactive elements, bond easily with other substances, unstable • Never found alone in nature • Lose 2 electrons to form stable +2 ions • Form ionic bonds • Combine with oxygen and other non-metals in the Earth’s crust

  14. Groups 3-12 The Transition Metals • 1 or 2 valence electrons • Can lose and/or share valence electrons • Common metals – gold, silver & copper • Form metallic bonds • Unpredictable

  15. From Metals to Nonmetals(e- in outer energy level) • Group 13 Boron Group/Family 3 valence electrons • Group 14 Carbon Group 4 valence electrons • Group 15 Nitrogen Group 5 valence electrons • Group 16 Oxygen Group 6 valence electrons • Group 17 Halogen Group 7 valence electrons • Group 18 Noble Gases 8 valence electrons * Helium is a Noble Gas but has a full outer shell with 2 valence e-

  16. Rare Earth Elements(Inner Transition Metals) • First Row –Lanthanide Series - Rare Earth metals - All but one is non-radioactive • Second Row – Actinide Series - Most are man-made and radioactive - Many are short-lived

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