Organizing Elements Chapter 6 Section 1 Organizing the

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Organizing Elements Chapter 6 Section 1

Organizing Elements Chapter 6 Section 1

Organizing the Elements • A few elements, such as gold and copper, have been

Organizing the Elements • A few elements, such as gold and copper, have been known for thousands of years - since ancient times • Yet, only about 13 had been identified by the year 1700. • As more were discovered, chemists realized they needed a way to organize the elements.

J. W. Dobereiner • A German chemist who published a classification system of the

J. W. Dobereiner • A German chemist who published a classification system of the known elements in 1829 • In his system, elements were grouped into triads (a set of 3 elements with similar properties). • One element in each triad had properties intermediate of the other two elements • Johann Wolfgang Dobereiner

Organizing • Chemists used the properties of elements to sort them into groups. •

Organizing • Chemists used the properties of elements to sort them into groups. • Chlorine, bromine, and iodine have very similar chemical properties.

Mendeleev’s Periodic Table • By the mid-1800 s, about 70 elements were known to

Mendeleev’s Periodic Table • By the mid-1800 s, about 70 elements were known to exist • Dmitri Mendeleev – a Russian chemist and teacher • Arranged elements in order of increasing atomic mass • Thus, the first “Periodic Table”

Mendeleev’s Periodic Table

Mendeleev’s Periodic Table

Mendeleev’s Periodic Table • He left blanks for yet undiscovered elements – When they

Mendeleev’s Periodic Table • He left blanks for yet undiscovered elements – When they were discovered, he had made good predictions • But, there were problems: –Such as Co and Ni; Ar and K; Te and I

A Better Arrangement • In 1913, Henry Moseley – British physicist, arranged elements according

A Better Arrangement • In 1913, Henry Moseley – British physicist, arranged elements according to increasing atomic number • The arrangement used today • The symbol, atomic number & mass are basic items included-textbook pg. 162 and 163

Periodic Law • The periodic law: When elements are arranged in order of increasing

Periodic Law • The periodic law: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. – The properties of the elements within a period change as you move across a period from left to right. – The properties of the elements within a group are the same as you move down a group

Periodic Law

Periodic Law

Areas of the periodic table • Three classes of elements are: 1) metals 2)

Areas of the periodic table • Three classes of elements are: 1) metals 2) nonmetals 3) metalloids

Metals • 80 percent of periodic table • Good conductor of heat and electric

Metals • 80 percent of periodic table • Good conductor of heat and electric current • All are solid at room temperature, except mercury which is a liquid • Most are malleable

Metals

Metals

Nonmetals • Most nonmetals are gases at room temperature, few are solids and bromine

Nonmetals • Most nonmetals are gases at room temperature, few are solids and bromine is the only liquid • Poor conductors of heat and electric current

Nonmetals

Nonmetals

Metalloids • The elements that border the stair step line that separates the metals

Metalloids • The elements that border the stair step line that separates the metals from the nonmetals are the metalloids • These can either behave like a metal or a nonmetal

Metalloids

Metalloids

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