Chapter 3 Atoms and Elements

3.1Classification of Matter

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Matter

Matter is the “stuff” that makes up all things.

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Pure SubstancesA pure substance is classified as

• matter with a specific composition.

• an element when composed of one type of atom.

• a compound when composed of two or more elements combined in a definite ratio.

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Elements

Elements are

• pure substances that contains atoms of only one type.

Copper, CuLead, PbAluminum, Al

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CompoundsCompounds

• contain two or more elements in a definite ratio.

Salt (NaCl)Table sugar

(C12H22O11)

Water (H2O)

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Elements in a Compound

“Table salt” is a compound that contains the elements sodium and chlorine.

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MixturesA mixture is a type of matter that consists of

• two or more substances that are physically mixed, not chemically combined.

• two or more substances in different proportions.

• substances that can be separated by physical methods.

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Physical Separation of a Mixture

Example: Pasta and water are separated with a

strainer.

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Homogeneous Mixtures

In a homogeneous mixture,

• the composition is uniform throughout.

• the different parts of the mixture are not visible.

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Heterogeneous Mixtures

In a heterogeneous mixture,

• the composition of substances is not uniform.

• the composition varies from one part of the mixture to another.

• the different parts of the mixture are visible.

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Classification of Matter

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ExampleIdentify each of the following as a pure substance or a mixture.

A. pasta and tomato sauce

B. aluminum foil

C. helium

D. air

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Learning Check

Identify each of the following as a homogeneous orheterogeneous mixture:

A. hot fudge sundae

B. air

C. sugar water

D. peach pie

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Chapter 3 Atoms and Elements3.2

Elements and Symbols

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ElementsElements are

• pure substances that cannot be separated into simpler substances by ordinary laboratory processes.

• the building blocks of matter.

gold carbon aluminum

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Sources of Some Element Names

Some elements arenamed for planets,mythological figures,minerals, colors,scientists, andplaces.

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Symbols of Elements

A symbol• represents the name of an element.

• consists of 1 or 2 letters.

• starts with a capital letter.

1-Letter Symbols 2-Letter Symbols

C carbon Co cobalt N nitrogen Ca

calcium F fluorine Al

aluminum O oxygen Mg

magnesium 17

Symbols from Latin Names

Several symbols are derived from Latin names as shownbelow.

Cu, copper (cuprum) Au, gold (aurum)

Fe, iron (ferrum) Ag, silver (argentum)

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Physical Properties of Elements

The physical properties of an element • are observed or measured without changing its

identity.• include the following:

Shape DensityColor Melting pointOdor and taste Boiling point

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Physical Properties of Elements

Some physical properties ofcopper are:

Color Red-orangeLuster Very shinyMelting point 1083 °CBoiling point 2567 °CConduction of electricity ExcellentConduction of heat Excellent

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Example

Select the correct symbol for each.A. Phosphorous

1) K 2) P 3) Ph

B. Aluminum 1) Al 2) Au 3) An

C. Iron 1) Ir 2) FE 3) Fe

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Learning Check

Select the correct name for each symbol.A. Ne

1) neon 2) nitrogen 3) nickel

B. K 1) potassium 2) phlogiston 3) phosphorus

C. Au 1) silver 2) agean 3) gold

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Chapter 3 Atoms and Elements3.3

The Periodic Table

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Mendeleev’s Periodic Table (1871)

Until the discovery of the proton, the elements were typically organized by increasing atomic weight.The modern organization is by increasing atomic number.

Groups and Periods

On the periodic table,

• elements are arranged according to similar properties.

• groups contain elements with similar properties in vertical columns.

• periods are horizontal rows of elements.

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Periods: 7 horizontal rows.

Groups: 18 vertical columns.International standard: 1-18US system: 1A-8A, 1B-8B

Groups and Periods

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Names of Some Representative Elements

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Group Numbers

Group Numbers

• use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements.

• also use numbers 1-18 to the columns from left to right.

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Alkali Metals

Group 1A (1), the alkali metals, includes lithium, sodium, and potassium.

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Halogens

Group 7A (17), the halogens, includes chlorine, bromine, and iodine.

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Examples

Identify the element described by the following:

A. Group 7A (17), Period 4 1) Br 2) Cl 3) Mn

B. Group 2A (2), Period 3 1) beryllium 2) boron 3)

magnesium

C. Group 5A (15), Period 2 1) phosphorus 2) arsenic 3) nitrogen

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Metals, Nonmetals, and Metalloids

The heavy zigzag line separates metals and nonmetals.

• Metals are located to the left.

• Nonmetals are located to the right.

• Metalloids are located along the heavy zigzag line between the metals and nonmetals.

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Metals, Nonmetals, and Metalloids on the Periodic Table

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Properties of Metals, Nonmetals, and MetalloidsMetals

•are shiny and ductile.

•are good conductors of heat and electricity.

Nonmetals•are dull, brittle, and poor conductors.

•are good insulators.Metalloids

•are better conductors than nonmetals, but not as good as metals.

•are used as semiconductors and insulators.

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Comparing a Metal, Metalloid, and Nonmetal

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Examples

Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid.

A. sodium ____B. iodine ____C. Argon ____D. iron ____E. Silicon ____

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Learning CheckMatch the elements to the description.

A. Metals in Group 4A (14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn

B. Nonmetals in Group 5A (15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb

C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb

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