Chapter 3Chapter 3Atoms and Atoms and ElementsElements

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3.1 Elements and Symbols3.1 Elements and Symbols

Elements 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 Sources of Some Element NamesNames

Some elements are

named for planets,

mythological figures,

minerals, colors,

scientists, and

places.

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TABLE 3.1

Symbols of ElementsSymbols 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 4

Symbols from Latin NamesSymbols from Latin Names

Several symbols are derived from Latin names as shown

below.

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

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

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Physical Properties of Physical Properties of ElementsElements

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 Physical Properties of ElementsElements

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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ExampleExample

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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ExamplesExamples

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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Development of the Periodic TableDevelopment of the Periodic Table

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.

3.3The Periodic Table3.3The Periodic Table

Groups and PeriodsGroups 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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Groups and PeriodsGroups and Periods

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Names of Some Representative Names of Some Representative ElementsElements

Group NumbersGroup 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.

Elements and the Periodic Elements and the Periodic TableTable

Alkali MetalsAlkali Metals

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

HalogensHalogens

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

ExamplesExamples

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 Metals, Nonmetals, and MetalloidsMetalloids

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 Metals, Nonmetals, and Metalloids on the Periodic TableMetalloids on the Periodic Table

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Properties of Metals, Nonmetals, Properties of Metals, Nonmetals, and Metalloidsand Metalloids

Metals • 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, Comparing a Metal, Metalloid, and Nonmetaland Nonmetal

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TABLE 3.4

Periods: 7 horizontal rows.

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

SUMMARY

ExamplesExamples

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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ExamplesExamples

Match 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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The Law of Multiple Proportions and Dalton’s The Law of Multiple Proportions and Dalton’s Atomic TheoryAtomic Theory

• Elements are made up of tiny particles called atoms.

• Each element is characterized by the mass of its atoms. Atoms of the same element have the same mass, but atoms of different elements have different masses.

• The chemical combination of elements to make different chemical compounds occurs when atoms join in small whole-number ratios.

• Chemical reactions only rearrange how atoms are combined in chemical compounds; the atoms themselves don’t change.

3.4 The Atom

Atomic Structure: ElectronsAtomic Structure: Electrons

Cathode-Ray Tubes: J. J. Thomson (1856-1940) proposed that cathode rays must consist of tiny negatively charged particles. We now call them electrons.

Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment

Copyright © 2009 by Pearson Education, Inc.

Rutherford’s Gold Foil Rutherford’s Gold Foil ExperimentExperiment

In Rutherford’s gold foil experiment, positively charged particles • were aimed at atoms of gold.• mostly went straight through the atoms. • were deflected only occasionally.

Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.

Subatomic ParticlesSubatomic Particles

Atoms contain subatomic particles.

• Protons have a positive (+) charge.

• Electrons have a negative (-) charge.

• Neutrons are neutral.

• Like charges repel and unlike charges attract.

Structure of the AtomStructure of the Atom

An atom consists

• of a nucleus that contains protons and neutrons.

• of electrons in a large, empty space around the nucleus.

Atomic Mass ScaleAtomic Mass Scale

On the atomic mass scale,

• 1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom.

• a proton has a mass of about 1 (1.007) amu.

• a neutron has a mass of about 1 (1.008) amu.

• an electron has a very small mass, 0.000 549 amu.

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Particles in the AtomParticles in the Atom

TABLE 3.5

ExamplesExamples

Identify each statement as describing a1) proton, 2) neutron, or 3) electron.

A. found outside the nucleusB. has a positive chargeC. is neutralD. found in the nucleus

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ExamplesExamples Is each of the following statements true or

false?◦ Protons are heavier than electrons◦ Protons are attracted to neutrons◦ Electrons are small that they have no

electrical charge◦ The nucleus contains all the protons and

neutrons of an atom

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