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

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:I. Atomic WeightII. Melting Pts.III. 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”

Meyer vs. Mendeleyev

• 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

Modern Russian Table

Spiral Periodic Table

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

Today’s Table

More History• First Elements Discovered:1. Carbon2. Sulfur3. Copper4. Gold & Silver5. Iron6. Tin7. Antimony8. Mercury9. Lead10. Oxygen (1772)

• First Classified Groups:1. Gases2. Non-Metals3. Metals4. Earths

1A

2A 3A 4A 5A 6A 7A

8A0• The elements in the A groups are called the representative elements

Transition metals

• The Group B elements

1A 2A

3A 4A 5A 6A 7A

8A

3B 4B 5B 6B 7B 8B 8B 8B 1B 2B

1 2

13 14 15 16 17

18

3 4 5 6 7 8 9 10 11 12

IA IIA

IIIB

IVB

VB

VIB

VIIB

VIIIB

IIIA

IVA

VA

VIA

VIIA

VIIIA

IB IIB

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

The group B are called the transition elements

These are called the inner transition elements and they belong here

Metals

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

Non-metals

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