Classification Of ElementsAnd

Periodicity In Properties

1) Dobereiner’s Triads2) A.E.B de Chancourtois’s Cylinder 3) John Newland’s Law Of Octaves4) Lothar Meyer’s Periodic Table 5) Mendeleev’s Periodic Table

6)Modern Periodic Table

What We Will Learn:

GERMAN CHEMIST JOHANN DOBEREINER

PROPOSED HIS CLASSIFICATION IN 1829

Dobereiner’s Triads

The Triads

The Triads

REASON FOR FAILURE:

THE LAW OF TRIADS SEEMED TO WORK ONLY FOR A FEW ELEMENTS AND THEREFORE IT WAS DISMISSED AS COINCIDENCE.

FRENCH GEOLOGISTA.E.B CHANCOURTOIS

PROPOSED HIS CLASS IN 1862

ENGLISH CHEMISTJOHN ALEXANDER NEWLANDS

PROPOSED IN 1865

Newland’sLaw Of Octaves

Law Of Octaves“If the elements are arranged in increasing order of their atomic weights, then every 8th element has propertiessimilar to that of the first"

REASON FOR FAILURE:

THE LAW OF OCTAVES WAS ONLY VALID UP TO CALCIUM.

LOTHAR MEYER DMITRI MENDELEEV

ON ARRANGING ELEMENTS IN INCREASING ORDER OF THEIR ATOMIC WEIGHTS, SIMILARITIES APPEAR IN PHYSICAL AND CHEMICAL PROPERTIES AT REGULAR INTERVALS.

GERMAN CHEMISTLOTHAR MEYERCLASSIFIED IN 1869

Lothar Meyer considered the following properties while arranging the elements:

•Atomic Volume•Melting Point•Boiling Point

RUSSIAN CHEMISTDMITRI MENDELEEV

Mendeleev’sPeriodic Law

“The Properties of the elements are a periodic function of their atomic weights”

Original Mendeleev’s table

Table highlighting the missing elements

The Modern Periodic Table

ENGLISH PHYSICISTHENRY MOSELEY

Hence proved that ATOMIC NUMBER was a more fundamental property ofan element than it’s atomic mass..

Graph of √v vs. Z

Modern Periodic Law

“The physical and chemical properties of the elements are the periodic functions of their atomic numbers”

The Endend.wmv