Where did it come from? Was is created or discovered?

The History of the Table

• In 1789 Antoine Antoine LavoisierLavoisier first defined a chemical element & drew up a table of 33 elements.

• He grouped these elements into 4 groups – Metals– Non-metals– Earths– Gases

The History of the Table

1829 1829 Johann Dobereiner Johann Dobereiner • Introduced his

Law of TriadsLaw of Triads

• This Law referred to groups of three chemically similar elements in which the properties of the middle element could be inferred from the lighter and heavier ones.

Triad Triad Triad

Lithium Lithium

Li Li SulfurSulfur

S S Chlorine Chlorine

ClCl

SodiumSodium

Na Na SeleniumSelenium

SeSeBromineBromine

BrBrPotassiumPotassium

KKTellurium Tellurium

TeTeIodineIodine

II

The History of the Table

• 1865 John Newlands1865 John Newlands

• Created a table of seven columns and entered his elements in increasing atomic masses.

• Due to misalignments he squeezed some elements into the same box.

• He called this arrangement the

Law of Law of OctavesOctaves.

Ca

Every 7Every 7thth element would element would repeat propertiesrepeat properties

Li Be B C N O F

Na Mg Al Si P S Cl

KCr/Fe

Co/Ni Cu/Zn SeAs Br

What is the Periodic Law

• Mendeleev, a Russian Chemist, was one of the first to be partially successful in arranging the known elements in the 1870's into a chart that would allow the prediction of properties. He arranged the 69 elements known in those days according to increasing atomic masses. The first Periodic Law proposed by him stated:

"The properties of the elements are a periodic function of their atomic masses"

The History of the Table• 1869 Mendeleev 1869 Mendeleev

discovered not designed discovered not designed the basis for the modern the basis for the modern periodic table.periodic table.

When Mendeleev arranged the known elements using his periodic law, he found that certain elements grouped themselves into vertical groupings. He used the chemical and physical property periodicity and atomic mass of the elements to organize the elements.

Mendeleev Genius was attributed to the fact he left gaps for undiscovered elements. He predicted the properties of the eka-aluminum (Gallium),eka-boron(Scandium) and eka-silicon (Germanium)

The History of the Table

• 1914 Moseley determined 1914 Moseley determined the Atomic # of elements. the Atomic # of elements.

• Moseley then proceeded to rearrange the elements according to increasing atomic numbers. Moseley's arrangement seemed to clear up the contradictions Mendeleev's arrangement.

• Moseley's periodic law is now considered the current Periodic Law.

““The properties of the elements are a The properties of the elements are a periodic periodic function of their atomic function of their atomic

numbers"numbers"

Sir William Ramsay

• With the discovery of He and Ar a new group had to be created. Ramsay proposed a new group to fit between group 17 and group 1 by 1900 the nobel gases were discovered,

defined and placed into the periodic table.

The History of the Table

• There are two special series of elements that occur right after the transition metal element Actinium (Actinides) and

Lanthanum(Lathanides). These special inner transition state metals were first rearranged by Dr. Glen

Seaborg in the 1950's. It caused quite a stir until it was pointed out and demonstrated that this arrangement seemed to predict the properties of several newly synthesized man-made elements. Dr. Seaborg's work is the third milestone in our quest to make order out of the elements.

1950 Glen Seaborg 1950 Glen Seaborg Proposed a change.Proposed a change.

The Modern Periodic Table1.1. The metals The metals which tend to have their atoms

losing electrons are to the left of the stair-step line

2.2. Non-metals Non-metals which tend to have their atoms gaining electrons during chemical change are found to the right of the stair-step line. 3.3. Metalloids Metalloids which tend to have their atoms sometimes losing and sometimes gaining electrons duringchemical change are generally found touching the stair-step line. 4.4. The Noble gases The Noble gases Discovered when Sir Ramsey electrified rarefied air and

these gases glowed. in neither lose or gain electrons keeping their stable octet. They are in group 18.

Nobel Gases

METALS

Non-Metals

Metalloids

Periodicity The TRENDS

““The representative The representative elements"elements" (Groups 1,2,13,14,15,16,17,18) follow general trends. The properties that are observed have their basis in the periodicity exhibited by the elements The Transitional MetalsThe Transitional Metals which include Seaborg’s Lanthanide and Actinide series follow many of the same trends with a few exceptions. Such as; ionic radii changes as they lose d shell e’.

Represetative

Represetative

Transitional

Inner Transitional