Unit #4: Periodic Unit #4: Periodic TableTable

Chapter 5Chapter 5

The Periodic TableThe Periodic Table

Origin of the TableOrigin of the Table

1. J.W. Dobereiner (early 1800’s) German1. J.W. Dobereiner (early 1800’s) German

a. observed that several elements a. observed that several elements could be organized into groups of could be organized into groups of three- three- called “called “triadstriads””

b. elements of each triad shared b. elements of each triad shared similar similar propertiesproperties

2. J.A.R Newlands (1865)- English2. J.A.R Newlands (1865)- English

a. arranged table according to a. arranged table according to atomic atomic massmass

b. observed periodicity of the b. observed periodicity of the elementselements

c. law of octaves: c. law of octaves: properties of properties of elements repeat every eighth elements repeat every eighth elementelement

3. Dmitri Mendeleev (1869)- Russian3. Dmitri Mendeleev (1869)- Russiana. Published first table that is the basis for today’s a. Published first table that is the basis for today’s periodic tableperiodic table

b. arranged elements by increasing b. arranged elements by increasing atomic massatomic mass

c. assigned elements with similar properties to the c. assigned elements with similar properties to the same same columnscolumns

d. predicted existence of missing elements based d. predicted existence of missing elements based on his tableon his table

e. problem: some elements did not fit according to e. problem: some elements did not fit according to their atomic mass and propertiestheir atomic mass and properties

- - I / TeI / Te- - Co / NiCo / Ni- - Ar / KAr / K

4. H.G.J. Moseley (1913)- English4. H.G.J. Moseley (1913)- Englisha. developed idea of atomic numbera. developed idea of atomic number

b. used x-rays to determine the atomic b. used x-rays to determine the atomic number of elementsnumber of elements

c. corrected Mendeleev’s table by c. corrected Mendeleev’s table by arranging elements according to atomic arranging elements according to atomic numbernumber, , notnot atomic atomic massmass

d. founded modern d. founded modern periodic lawperiodic law: : when when elements are arranged in order of elements are arranged in order of increasing atomic number, their increasing atomic number, their physical and chemical properties show physical and chemical properties show a periodic patterna periodic pattern

B. Reading the TableB. Reading the Table1. Be familiar with the location of:1. Be familiar with the location of:

a. Alkali metalsa. Alkali metalsb. Alkaline earth metalsb. Alkaline earth metalsc. Metalloidsc. Metalloidsd. Transition metalsd. Transition metalse. Nitrogen familye. Nitrogen familyf. Oxygen familyf. Oxygen familyg. Halogensg. Halogensh. Noble gasesh. Noble gasesi. s, p, d, f blocksi. s, p, d, f blocksj. Horizontal rows- period or seriesj. Horizontal rows- period or seriesk. Veritcal columns- group or familyk. Veritcal columns- group or familyl. Most probable charge and outer shell l. Most probable charge and outer shell

configurationconfiguration

C. Periodic TrendsC. Periodic Trends

1. Atomic Radius1. Atomic Radius

a. a. the distance from the the distance from the center of center of an atom’s nucleus to an atom’s nucleus to its outer its outer most electronmost electron

decrease

incre

as

e

Decrease – Left Right

Increase – Top Bottom

2. Ionic Radius2. Ionic Radiusa. no clear trenda. no clear trendb. take in electronb. take in electron

- - ionic radius increasesionic radius increases- + - + charged nucleus is charged nucleus is

attracting attracting more electronsmore electrons- full outer shell results in - full outer shell results in

increased increased repulsion among electronsrepulsion among electronsc. remove electronc. remove electron

- - ionic radius decreasesionic radius decreases- + - + charged nucleus is charged nucleus is

attracting attracting fewer electronsfewer electrons

3. Ionization Energy3. Ionization Energy

a. Energy required to move an a. Energy required to move an electronelectron increase

incre

as

e

Increase – Left Right

Top Bottom

4. Electronegativity4. Electronegativity

a. an atom’s ability to attract a. an atom’s ability to attract electrons electrons in a chemical in a chemical bondbond

increase

incre

ase

Increase – Left Right

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