Organizing the Organizing the ElementsElements

The Periodic TableThe Periodic Table

Early GreeksEarly Greeks

Four classical Four classical elements: earth, elements: earth, water, wind, and water, wind, and fire.fire.

Correspond with Correspond with solid, liquid, gas, solid, liquid, gas, and plasma.and plasma.

ElementsElements

A few elements have been known for A few elements have been known for thousands of years: copper, silver, and thousands of years: copper, silver, and gold.gold.

Only 13 elements were discovered by the Only 13 elements were discovered by the year 1700.year 1700.

When chemists started using the scientific When chemists started using the scientific method, the rate increased to finding 5 method, the rate increased to finding 5 new elements in 10 years. new elements in 10 years.

Chemists needed a way to organize the Chemists needed a way to organize the elements- used the properties of the elements- used the properties of the elements to sort them into groups.elements to sort them into groups.

J.W. Dobereiner (1780-1849)J.W. Dobereiner (1780-1849)German ChemistGerman Chemist Published a Published a

classification system classification system where elements were where elements were put into triads. put into triads.

A triad is a group of 3 A triad is a group of 3 elements with similar elements with similar properties. properties.

An example of on such An example of on such triad is chlorine, triad is chlorine, bromine, and iodine. bromine, and iodine.

Chlorine, Bromine, and Chlorine, Bromine, and IodineIodine

Chlorine Gas

Liquid Bromine

Iodine

Chlorine, Bromine and Chlorine, Bromine and IodineIodine

Look different or have different Look different or have different physical properties.physical properties.

Have similar chemical properties.Have similar chemical properties.-all react easily with metals.-all react easily with metals.

The average atomic masses of The average atomic masses of chlorine and iodine is 81.177 amu. chlorine and iodine is 81.177 amu. This is close to bromine which is in This is close to bromine which is in the middle of the other two.the middle of the other two.

Dmitri MendeleevDmitri Mendeleev

Russian chemist in Russian chemist in 1869 who 1869 who published a chart published a chart of elementsof elements

Arranged the Arranged the elements in order elements in order of increasing of increasing atomic massatomic mass

Mendeleev’s Periodic TableMendeleev’s Periodic Table

Mendeleev put Mendeleev put question marks question marks where he predicted where he predicted elements should elements should be.be.

He predicted their He predicted their properties as well properties as well as their position on as their position on the periodic table. the periodic table.

Henry MoseleyHenry Moseley

1913, determined 1913, determined an atomic number an atomic number for each elementfor each element

Helped arrange the Helped arrange the periodic table in periodic table in order of increasing order of increasing atomic number.atomic number.

Periodic LawPeriodic Law

When elements are arranged in order of When elements are arranged in order of increasing atomic number, there is a increasing atomic number, there is a periodic repetition of their physical and periodic repetition of their physical and chemical properties.chemical properties.

Summary QuestionsSummary Questions

What are the 4 classical elements? What are the 4 classical elements? (early greeks)(early greeks)

Who was the first to try and arrange a Who was the first to try and arrange a periodic table?periodic table?

How did Mendeleev’s periodic table How did Mendeleev’s periodic table differ from the modern periodic table?differ from the modern periodic table?

What did Henry Moseley contribute to What did Henry Moseley contribute to the periodic table?the periodic table?