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Periodic Table. History. Antoine Lavoisier – Father of Modern Chemistry 1829 German J. W. Dobereiner Grouped elements into triads Three elements with similar properties Properties followed a pattern The same element was in the middle of all trends Not all elements had triads.
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History • Antoine Lavoisier – Father of Modern Chemistry • 1829 German J. W. Dobereiner Grouped elements into triads • Three elements with similar properties • Properties followed a pattern • The same element was in the middle of all trends • Not all elements had triads
Law of Octaves • 1862 John Newlands developed Law of Octaves • The elements showed a repetition in their chemical properties after 8 elements • Used Atomic Weights but not actual values • Important because showed the first pattern of repeating properties
Julius Lothar Meyer • Meyer first table published 1864 containing 28 elements • Arranged in order of Atomic Weight and made a clear horizontal relationship • Allowed properties (valency) to outweigh Atomic Weight • Anticipated Mendeleev by years
Meyer • Left gaps to denote unknown elements • Not willing to make predicitions • More focused on Physical properties not chemical properties • Bitter battle with Mendeleev • Lost to Mendeleev because of Mendeleev’s forceful ways
History • Russian scientist Dmitri Mendeleev taught chemistry in terms of properties • Mid 1800 – atomic masses of elements were known • Wrote down the elements in order of increasing mass • Found a pattern of repeating properties • Not first to develop system but his version had the strongest impact
Mendeleev’s Table • Grouped elements in columns by similar properties in order of increasing atomic mass • Found some inconsistencies - felt that the properties were more important than the mass, so switched order. • Found some gaps • Must be undiscovered elements • Predicted their properties before they were found
Dmitri Mendeleyev • Mendeleyev was known as the “Father of the Periodic Table” • DOB: 1834-1907 • Created the first table on 3-1-1869 • Table had 70 elements • Used properties to set up table
Mendeleev • Distinguished from competitors by a devotion to, and love for, the individuality of the elements that went hand in hand with an intimate knowledge of their chemical characteristics • Focused on both physical and chemical properties
Mendeleyev Cont. • Properties Used: • Atomic Weight • Melting Pts. • Densites • He could only predict these properties • His work preceded chemical advances by 30 years • Produced his table 27 years before the first subatomic particle, the electron was discovered • Did not predict Noble Gases
Acceptance • Mendeleev’s table received real acceptance in 1875 • Discovery of Scandium, Germanium and Gallium showed Mendeleev’s predictions were correct.
“The elements were not being arranged to make a periodic table, but to fit the periodic table”
Julius Meyer (1830-1895) Created a table that plotted: Atomic Volume vs. Atomic Weight Lost out to Mendeleyev Published before Meyer Final Table: Atomic Weight vs. Valency Table had 8 columns but was missing Noble Gases Discovered 30 years later Meyer vs. Mendeleyev
Changing of Table • Henry Moseley (1887-1915) – changed table in 1913 by increasing atomic number • Currently use this today • Glenn Seaborg – rare earth series from Actinium (89) up. • Minor Changes – inner transitional Lu & Lr replaced La & Ac • Bohr first linked Quantum Theory
First Elements Discovered: Carbon Sulfur Copper Gold & Silver Iron Tin Antimony Mercury Lead Oxygen (1772) First Classified Groups: Gases Non-Metals Metals Earths More History
8A0 1A 2A 3A 4A 5A 6A 7A • The elements in the A groups are called the representative elements
Transition metals • The Group B elements
VIIIB IA IIA VIB VIIB IIIB IVB VB 1 1A 2 2A 8A 18 13 3A 14 4A 15 5A 16 6A 7A 17 VIIIA VIA VIIA IIIA IVA VA IB IIB 3 3B 4B 4 5 5B 6B 6 7 7B 8 8B 9 8B 10 8B 1B 11 2B 12 Other Systems
Vertical Columns • Known as Groups or a Family • Elements in same group have similar physical & chemical properties • Each group is identified by a group number and group letter
Horizontal rows are called periods • There are 7 periods
Group 1A are the alkali metals • Group 2A are the alkaline earth metals
Group 7A is called the Halogens • Group 8 are the noble gases
These are called the inner transition elements and they belong here The group B are called the transition elements
Metals & Their Properties • Metals are good conductors of heat and electricity • Metals are malleable • Metals have high luster
Example of Metals • Copper is a relatively soft metal and a very good electrical conductor • Mercury is the only metal that exists as a liquid at room temperature
Nonmetals & Their Properties • Carbon, the graphite in a pencil is an example of a nonmetallic elements • Nonmetals are poor conductors of electricity • Can be brittle • Non-lustrous • Many are gases at room temperature
Example of Nonmetals • Sulfur was once known as Brimstone • Microspheres of phosphorus, a reactive nonmetal
Metalloids or Semimetals • Properties of both • Semiconductors
Example of a Metalloid • Silicon is a metalloid • Silicon is brittle like a nonmetal • Silicon has metallic luster • Silicon is a semiconductor of electricity
