The Periodic Table Chapter 4

4-1 What makes a group of elements?  Dobereiner  Triads – groups of three elements with similar chemical properties and middle element has atomic mass that is the average of first and third elements.  Newlands  Law of Octaves - arranged first 16 elements in order of increasing atomic mass (excluding hydrogen and noble gases). He discovered that chemical and physical properties repeated with every eighth element.

4-1 What makes a group of elements?  Dimitri Mendeleev – Periodic Law  First orderly arrangement of the known 63 elements in 1870  Arranged elements by increasing atomic mass  Left gaps so elements with similar chemical and physical properties could be in the same column.  Predicted properties of these yet undiscovered elements and was found to be correct when elements were finally discovered.

4-1 What makes a group of elements?  There were exceptions in Mendeleev’s table of elements. He felt it was more important to have elements group by properties than by increasing atomic mass.  Henry Mosley discovered atomic number (number of protons in nucleus) using x-ray diffraction and now PTE is arranged by increasing atomic number (Modern Periodic Law)

4-1 What makes a group of elements?  Overview of the modern periodic table  Period - a series of elements that form a horizontal row  Group – a series of element that form a vertical column (also referred to as a family)  All elements can be classified as a metal, non-metal or metalloid  Most of the elements on the PTE are metals

4-1 What makes a group of elements?  Properties of metals  Solid at room temperature  Shine (have luster)  Malleable  Ductile  Conduct electricity and heat  React with acid to form hydrogen gas  Found on the left and middle of the PTE

4-1 What makes a group of elements?  Properties of nonmetals  Dull  Brittle  Solid, liquid or gas at room temperature  Do not conduct electricity or heat  Do not react with acids

4-1 What makes a group of elements?  Properties of metalloids  Exhibit properties of both metals and nonmetals  They are in transition between metals and non metals so can act as either

4-1 What makes a group of elements?  Main Group Elements  Groups 1,2,13-18 are referred to as main group elements.  Electron configurations are consistent and all elements in the group react in a similar fashion.  Also called representative elements  Many have family names

4-1 What makes a group of elements?  Hydrogen is in its own family  Most common element in the universe  Has just one proton and one electron  Reacts with many elements, including oxygen  Is a component of all hydrocarbons as well as molecules that are essential to the chemistry of life (proteins, carbohydrates, fats, lipids)

4-2 What gives metals their distinctive properties?  Metals are able to ………  conduct electricity and heat  Shine  Malleable  Ductile  React with acids  Solid at room temp……  Because they have delocalized electrons. The more delocalized electrons a metal has, the more “metallic” it appears