6.1 Organizing the Elements

Section 6-1

• In a self-service store, the products are grouped according to similar characteristics. With a logical classification system, finding and comparing products is easy. You will learn how elements are arranged in the periodic table and what that arrangement reveals about the elements.

• Searching For an Organizing Principle

– How did chemists begin to organize the known elements?

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

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– Chlorine, bromine, and iodine

• have very similar chemical properties

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• Mendeleev’s Periodic Table

– How did Mendeleev organize his periodic table?

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– Mendeleev arranged the elements in his periodic table in order of increasing atomic mass.

– The periodic table can be used to predict the properties of undiscovered elements.

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• An Early Version of Mendeleev’s Periodic Table 6.1

• The Periodic Law

– How is the modern periodic table organized?

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• In the modern periodic table, elements are arranged in order of increasing atomic number.

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• 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 pattern of properties within a period repeats as you move from one period to the next.

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– What are three broad classes of elements?

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– Three classes of elements are:

• metals

• Nonmetals

• metalloids.

– Across a period, the properties of elements become:

• less metallic

• more nonmetallic.

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less metallic

more nonmetallic

» Metals, Metalloids, and Nonmetals in the Periodic Table

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» Metals, Metalloids, and Nonmetals in the Periodic Table

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• Metals

– Metals

• good conductors of heat and electric current.

• 80% of elements are metals.

• Metals:

– Have high luster

– are ductile

– are malleable

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» Uses of Iron, Copper, and Aluminum

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» Uses of Iron, Copper, and Aluminum

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• Nonmetals – are poor conductors of heat and electric current.

– Most nonmetals are gases at room temperature.

– A few nonmetals are solids • Sulfur

• phosphorus.

– One nonmetal is a dark-red liquid • bromine

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• Metalloid

– generally has properties that are similar to those of metals and nonmetals.

– The behavior of a metalloid can be controlled by changing conditions.

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• If a small amount of boron is mixed with silicon – the mixture is a good conductor of electric current.

– silicon can be cut into wafers

– and used to make computer chips.

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Quiz

1. The modern periodic table has elements arranged in order of

A. colors.

B. melting and boiling points.

C. increasing atomic mass.

D. increasing atomic number.

2. Mendeleev arranged the elements in his periodic table in order of increasing

A. atomic number.

B. number of protons.

C. number of electrons.

D. atomic mass

3. Which one of the following is NOT a general property of metals?

A. ductility

B. malleability

C. having a high luster

D. poor conductor of heat and electricity

END