History of the Periodic Table

John Newland – Law of Octaves

Dmitri Mendeleev 1869 – only 63 known elements Ranked elements by atomic mass (generally)

Dmitri Mendeleev Predicted the existence and properties of elements PREDICTED ACTUAL

Lord Rayleigh – Noble Gases 1895 – first noble gas discovered. Argon – nonreactive. Placed at the end of the table. He Ne Kr Ar Xe

Noble Gases Non-reactive because they have EIGHT valence electrons REMEMBER: VALENCE electrons are the electrons in the outermost shell that determine an element’s reactivity.

Elements and compounds WANT to have a full outer electron shell. Octet Rule The octet rule states that elements gain or lose electrons until they have an electron configuration like the nearest noble gas. Elements and compounds WANT to have a full outer electron shell.

Glenn Seaborg Last change to the periodic table 1940 – discovered plutonium and all elements from 94 to 102 Moved the Actinide and Lanthanide series beneath the table

Modern Table Arranged by atomic number: Increasing number of protons (and therefore electrons in neutral atoms). Contains Periods and Groups

Periodicity A pattern that repeats – in this case, repeating properties of elements Periods are HORIZONAL rows Period 1  Period 2  Period 3  Period 4  Period 5  Period 6  Period 7 

Groups The vertical columns of the periodic table Also called “Families”

Groups Elements in groups share similar properties We’ll get into the details of this later. 

Write down any questions that you have about the periodic table. Exit Slip Write down any questions that you have about the periodic table.