Presentation on theme: "The History and Arrangement of the Periodic Table."— Presentation transcript:
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 ► Made each element a card and listed its properties known at the time (mass, density, color, melting point and valence number).
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.
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.
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).
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
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
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
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
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
► 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? Group (Family) 1 - Alkali Metals
Hydrogen is a nonmetal gas and forms covalent bonds. So why is it in the Alkali Metal family? ► The number of valence electrons = 1
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
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
From Metals to Nonmetals (e - in outer energy level) ► Group 13Boron Group/Family3 valence electrons ► Group 14Carbon Group4 valence electrons ► Group 15Nitrogen Group5 valence electrons ► Group 16Oxygen Group6 valence electrons ► Group 17Halogen Group7 valence electrons ► Group 18Noble Gases8 valence electrons * Helium is a Noble Gas but has a full outer shell with 2 valence e -
Rare Earth Elements (Inner Transition Metals) ► First Row –Lanthanide Series - Rare Earth metals - Rare Earth metals - All but one is non-radioactive - All but one is non-radioactive ► Second Row – Actinide Series - Most are man-made and radioactive - Many are short-lived