History of Periodic Table

History of Periodic Table

-In the beginning: discover elements 52 by 1817, 62 by 1863

 Some kinds of organizations were needed:

·         First attempt done in 1820’s

·         1857 William Ordling separated the known elements into 13 groups based on their physical and chemical properties. (It was a start)

·         Between 1863 and 1866 John Newlands assigning Hydrogen -mass1 and ordering the known elements by their masses, every eighth element shared a common set of properties

(“Law of octaves”). Weaknesses: cannot predict elements, and he kept changing the orders

·         1869- Dimitri Mendeleev published a method of organizing the elements according to both their masses and their properties. The elements are listed according to masses, certain properties recur PERIODICALLY. (Rows (PERIOD) and columns (GROUP).)

-can accurately predict elements

-chemists can understand and organize data and predict new properties

Modern periodic table

·         Is organized according to atomic number rather than atomic mass.

·         The periodic law summarizes the periodic table. The Periodic Law: Properties of the chemical elements recur periodically when the elements are arranged from lowest to highest atomic numbers

 Period: The set of all elements in a given row going across the table.

Group or Family: The set of all elements in a given column going down the table.

Alkali Metal = elements in the first column (Except H)

Alkaline Earth Metals = The elements in the second column

Halogens = second column from the end on the right hand side. Starting with Fluorine.

Noble Gases = Far right side of the table. Starting with helium.

Lanthanides = elements in the first row shown underneath the table. Starting with lanthanum.

Actinides = underneath the Lanthanides. Starting with actinium.

·         Metals, non-metals, semiconductor