Chemistry 1-5: An Overview of the Periodic Table

• Describe how the Periodic table was made and has been changed over time

• Identify the different parts of the periodic table and what they signify

• Compare and Contrast Different types of elements

Development of the Periodic Table

• Throughout History, different Elements have been discovered at different times

  • 1700: Only 13 Elements were known to exist​

    • Some chemists thought others existed, but could not directly prove them

    • Scientists began to sort out and arrange elements based on patterns

      • Hard to decide which pattern to follow

J.W. Dobereiner

• German Chemist

• 1829: Sorted Elements into groups of three

  • Found that he could arrange it so the middle element was always a midway point between the 1st and 2nd element​

    • Example: Atomic Masses

John Newlands

• English scientist

• 1865: Organized the known 56 elements by atomic weight

  • Proposed the Law of Octaves: every eighth element​ is similar to the first

Dimitri Mendelev

• Russian Chemist

• 1896: Tried to organize elements based on properties into a book he was writing

  • ​Placed the name of each element on a card with the atomic mass and a list of properties

  • ​Noticed when cards were arranged by mass, certain similarities appeared at regular intervals

• ​Periodic: A repeating pattern

  • Even though this pattern worked, there were some places where he switched certain elements to make the patterns line up

    • Switched tellurium and iodine

Dimitri Mendelev's Table

• Mendeleev’s Table had open spaces because not all of the elements were discovered in 1869,

  • He predicted what they would be like according to his table

    • ​In 1886 Three elements were found that matched his predictions

      • ​Scandium Sc

      • ​Gallium Ga

      • ​Germanium Ge

    • ​Because of his accurate predictions, Mendelev is credited as the father of the periodic law

The Modern Periodic Table

• Mendeleev’s Table was formed before scientists understood the structure of the atom

  • Organizing by atomic mass had some inconsistencies, but when he switched elements to fit by properties,he wound up putting them in order of atomic number

• The Modern Periodic Table is arranged by atomic number

Parts of the The Modern Periodic Table

• Period: A Horizontal row of a periodic table

  • The properties of elements change as you move across a period

  • Periodic Law: When elements are arranged in order of increasing atomic number, there is a repetition of their physical and chemical properties​

• Group: A vertical Column of the periodic table

  • Elements in the same group share physical and chemical properties

Parts of the The Modern Periodic Table

Types of Elements in the periodic Table

• ​Elements are classified into types

  • Metals

  • Metalloids

  • Nonmetals

• As you move across a period, elements become less metallic and more nonmetallic​

Metals

• about 80% of the elements are metals

• Except for Mercury, all metals are solid at room temperature

• Are good at conducting Heat and Electricity

• Reflect light

• Malleable: able to be hammered into shapes without breaking

• Ductile: Able to be pulled and stretched into wires​

Metalloids

• Elements with properties between those of metals and nonmetals

  • Are solids at room temperature

  • do not shine

• Individually are poor conductors of heat and electricity, but when combined with other metalloids become good conductors

  • Many electronic parts depend on metalloids as semi-conductors​

Nonmetals

• Tend to be poor at conducting heat and electric current

  • Exception: Carbon

• Are brittle​

The Modern Periodic Table

• All modern periodic tables include the 118 known elements

• Other information can vary from table to table​

• Main Group Elements

  • The s & p block Elements

  • Display a wide range in their chemical and physical properties​