Table of Contents Chapter 3 Atoms: The Building Blocks of Matter Section 1 The Atom: From Philosophical Idea to Scientific Theory Section 2 The Structure

Table of Contents

Chapter 3 Atoms: The Building Blocks of Matter

Section 1 The Atom: From Philosophical Idea to Scientific Theory Section 2 The Structure of the Atom

Section 3 Counting Atoms

Unit 1 • Investigation III

DO NOWDO NOW

In the 5In the 5thth century BCE a Greek century BCE a Greek philosopher named Leucippus philosopher named Leucippus and his student, Democritis, and his student, Democritis, stated, “All matter is made up stated, “All matter is made up of particles that can be divided of particles that can be divided called atoms.”called atoms.”

What do you think atoms are? What do you think atoms are?

ObjectivesObjectives

Introduction to the Introduction to the atom and its modelsatom and its models

Investigate various Investigate various historical models of the historical models of the atomatom

Definition of atom, size Definition of atom, size and structuresand structures


Atoms are extremely small Atoms are extremely small particles, which cannot be particles, which cannot be seen, even with microscopes.seen, even with microscopes.All matter is made up of All matter is made up of atoms.atoms.Scientists have created Scientists have created models to describe atoms. models to describe atoms. Models are similar to theories, Models are similar to theories, but often include a picture or but often include a picture or physical representation.physical representation.


•Five Models of the AtomFive Models of the Atom

(cont.)

Models / Models / ScientistsScientistsDalton --------- BDalton --------- B

J.J Thompson ---------- DJ.J Thompson ---------- D

Rutherford or Nuclear --------- ARutherford or Nuclear --------- A

Bohr ----------- Bohr ----------- EE

Quantum ----------- CQuantum ----------- C

ModelsModelsIts possible to remove a negatively Its possible to remove a negatively charged particle from an atom using charged particle from an atom using electrical forces. (J. J. Thompson, 1897)electrical forces. (J. J. Thompson, 1897)

If a tiny particle is shot into a middle of an If a tiny particle is shot into a middle of an atom. It hits something dense in the atom. It hits something dense in the center and bounces back in the direction center and bounces back in the direction it came from. If a tiny particle is shot into it came from. If a tiny particle is shot into the edges of the atom, it goes through. the edges of the atom, it goes through. Most tiny particles shot in an atom will go Most tiny particles shot in an atom will go through. (Rutherford,1911)through. (Rutherford,1911)

The farther away from the center of an The farther away from the center of an atom the negatively charged particles, are atom the negatively charged particles, are the easier they are to remove. (Bohr, the easier they are to remove. (Bohr, 1913)1913)


An atom is mostly empty An atom is mostly empty space.space.The rest consists of a The rest consists of a nucleus, which is located in nucleus, which is located in the very center of the the very center of the atom, and electrons, which atom, and electrons, which are located around the are located around the nucleus.nucleus.The nucleus is very small The nucleus is very small


The nucleus is also very dense The nucleus is also very dense and consists of two types of and consists of two types of particles—neutrons and protons.particles—neutrons and protons.A neutron is a neutral particle A neutron is a neutral particle with no charge on it.with no charge on it.A proton is a positively charged A proton is a positively charged particle.particle.Tightly bound together, Tightly bound together, neutrons and protons make a neutrons and protons make a positively charged nucleus.positively charged nucleus.

Section 1 The Atom: From Philosophical Idea to Scientific Theory

ObjectivesObjectives• ExplainExplain the the law of conservation of mass, law of conservation of mass, the the law of definite law of definite

proportions,proportions, and the and the law of multiple proportions.law of multiple proportions.

• SummarizeSummarize the five essential points of Dalton’s atomic theory. the five essential points of Dalton’s atomic theory.

• ExplainExplain the relationship between Dalton’s atomic theory and the the relationship between Dalton’s atomic theory and the law of conservation of mass, the law of definite proportions, and law of conservation of mass, the law of definite proportions, and the law of multiple proportions.the law of multiple proportions. The transformation of a substance The transformation of a substance or substances into one or more new substances is known as a or substances into one or more new substances is known as a chemical reactionchemical reaction..

• Law of conservation of mass:Law of conservation of mass: mass is neither created nor mass is neither created nor destroyed during ordinary chemical reactions or physical changesdestroyed during ordinary chemical reactions or physical changes

Chapter 3


Foundations of Foundations of Atomic TheoryAtomic Theory

• The transformation of a substance or The transformation of a substance or substances into one or more new substances into one or more new substances is known as a substances is known as a chemical chemical reactionreaction..

• Law of conservation of mass:Law of conservation of mass: mass is mass is neither created nor destroyed during neither created nor destroyed during ordinary chemical reactions or physical ordinary chemical reactions or physical changeschanges

Chapter 3

Visual Concepts

Chemical ReactionChemical Reaction

Chapter 3


Foundations of Atomic Foundations of Atomic Theory Theory

• Law of definite proportions:Law of definite proportions: a chemical a chemical compound contains the same elements in compound contains the same elements in exactly the same proportions by mass exactly the same proportions by mass regardless of the size of the sample or regardless of the size of the sample or source of the compoundsource of the compound

• Law of multiple proportions:Law of multiple proportions: if two or more if two or more different compounds are composed of the different compounds are composed of the same two elements, then the ratio of the same two elements, then the ratio of the masses of the second element combined with masses of the second element combined with a certain mass of the first element is always a certain mass of the first element is always a ratio of small whole numbersa ratio of small whole numbers

Chapter 3

Law of Law of ConservConservation of ation of

MassMass

Section 1 The Atom: From Philosophical Idea to Scientific TheoryChapter 3

Law of Multiple Law of Multiple ProportionsProportions

Section 1 The Atom: From Philosophical Idea to Scientific TheoryChapter 3


Dalton’s Atomic Dalton’s Atomic TheoryTheory• All matter is composed of extremely small All matter is composed of extremely small

particles called atoms.particles called atoms.

• Atoms of a given element are identical in size, Atoms of a given element are identical in size, mass, and other properties; atoms of different mass, and other properties; atoms of different elements differ in size, mass, and other elements differ in size, mass, and other properties.properties.

• Atoms cannot be subdivided, created, or Atoms cannot be subdivided, created, or destroyed.destroyed.

Chapter 3


Dalton’s Atomic Dalton’s Atomic TheoryTheory

• Atoms of different elements combine in Atoms of different elements combine in simple whole-number ratios to form simple whole-number ratios to form chemical compounds.chemical compounds.

• In chemical reactions, atoms are In chemical reactions, atoms are combined, separated, or rearranged.combined, separated, or rearranged.

Chapter 3


Modern Atomic Modern Atomic TheoryTheory• Not all aspects of Dalton’s atomic theory Not all aspects of Dalton’s atomic theory

have proven to be correct. We now know have proven to be correct. We now know that:that:

Chapter 3

Some important concepts remain unchanged.

• Atoms are divisible into even smaller particles.• A given element can have atoms with different masses.

• All matter is composed of atoms.• Atoms of any one element differ in properties from

atoms of another element.

Section 2 The Structure of the Atom

Lesson StarterLesson Starter• Even though the two shapes look different, Even though the two shapes look different,

the characteristics of the various parts the characteristics of the various parts that compose them are the same.that compose them are the same.

• The same is true with the atom.The same is true with the atom.

• Though atoms of different elements Though atoms of different elements display different properties, isolated display different properties, isolated subatomic particles have the same subatomic particles have the same properties.properties.

Chapter 3


ObjectivesObjectives• SummarizeSummarize the observed properties of cathode the observed properties of cathode

rays that led to the discovery of the electron.rays that led to the discovery of the electron.

• SummarizeSummarize the experiment the experiment carried out by carried out by Rutherford and his co-workers that led to the Rutherford and his co-workers that led to the discovery of the nucleus.discovery of the nucleus.

• ListList the properties of protons, neutrons, and the properties of protons, neutrons, and electrons.electrons.

• Define Define atom.atom.

Chapter 3


The Structure of the The Structure of the AtomAtom

• An An atomatom is the smallest particle of an element is the smallest particle of an element that retains the chemical properties of that that retains the chemical properties of that element.element.

• The The nucleusnucleus is a very small region located at the is a very small region located at the center of an atom.center of an atom.

• The nucleus is made up of at least one positively The nucleus is made up of at least one positively charged particle called a charged particle called a protonproton and usually one and usually one or more neutral particles called or more neutral particles called neutronsneutrons..

Chapter 3


The Structure of the The Structure of the AtomAtom

• Surrounding the nucleus is a region Surrounding the nucleus is a region occupied by negatively charged particles occupied by negatively charged particles called called electronselectrons..

• Protons, neutrons, and electrons are often Protons, neutrons, and electrons are often referred to asreferred to as subatomic particlessubatomic particles..

Chapter 3

Visual Concepts

AtomAtom

Chapter 3

Properties of Properties of Subatomic ParticlesSubatomic Particles

Section 2 The Structure of the AtomChapter 3


Discovery of the Discovery of the ElectronElectronCathode Rays and ElectronsCathode Rays and Electrons

Chapter 3

Experiments in the late 1800s showed that cathode rays were composed of negatively charged particles.

These particles were named electrons.


Discovery of the Discovery of the ElectronElectron

Joseph John Thomson’s cathode-ray tube Joseph John Thomson’s cathode-ray tube experiments measured the charge-to-mass ratio experiments measured the charge-to-mass ratio of an electron.of an electron.

Chapter 3

Charge and Mass of the Electron

With this information, scientists were able to determine the mass of an electron.

Robert A. Millikan’s oil drop experiment measured the charge of an electron.


Discovery of the Discovery of the Electron, Electron, continuedcontinued

Chapter 3


Discovery of the Discovery of the Atomic NucleusAtomic Nucleus

• More detail of the atom’s structure was More detail of the atom’s structure was provided in 1911 by Ernest Rutherford and his provided in 1911 by Ernest Rutherford and his associates Hans Geiger and Ernest Marsden.associates Hans Geiger and Ernest Marsden.

• The results of their The results of their gold foil experimentgold foil experiment led to led to the discovery of a very densely packed bundle the discovery of a very densely packed bundle of matter with a positive electric charge.of matter with a positive electric charge.

• Rutherford called this positive bundle of Rutherford called this positive bundle of matter the matter the nucleusnucleus..

Chapter 3

Gold Foil Gold Foil ExperimentExperiment


Gold Foil Experiment Gold Foil Experiment on the Atomic Levelon the Atomic Level



Composition of the Composition of the Atomic NucleusAtomic Nucleus

• Except for the nucleus of the simplest type of Except for the nucleus of the simplest type of hydrogen atom, all atomic nuclei are made of hydrogen atom, all atomic nuclei are made of protonsprotons and and neutrons.neutrons.

• A proton has a positive charge equal in A proton has a positive charge equal in magnitude to the negative charge of an electron.magnitude to the negative charge of an electron.

• Atoms are electrically neutral because they Atoms are electrically neutral because they contain equal numbers of protons and electrons.contain equal numbers of protons and electrons.

• A neutron is electrically neutral.A neutron is electrically neutral.

Chapter 3


Composition of the Composition of the Atomic NucleusAtomic Nucleus

• The nuclei of atoms of different elements The nuclei of atoms of different elements differ in their number of protons and differ in their number of protons and therefore in the amount of positive therefore in the amount of positive charge they possess.charge they possess.

• Thus, the number of protons determines Thus, the number of protons determines that atom’s identity.that atom’s identity.

Chapter 3


• When two protons are extremely close to each When two protons are extremely close to each other, there is a strong attraction between them.other, there is a strong attraction between them.

Chapter 3

Forces in the Nucleus

The short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together are referred to as nuclear forces.

A similar attraction exists when neutrons are very close to each other or when protons and neutrons are very close together.


The Sizes of AtomsThe Sizes of Atoms• The radius of an atom is the distance The radius of an atom is the distance

from the center of the nucleus to the from the center of the nucleus to the outer portion of its electron cloud.outer portion of its electron cloud.

• Because atomic radii are so small, they Because atomic radii are so small, they are expressed using a unit that is more are expressed using a unit that is more convenient for the sizes of atoms.convenient for the sizes of atoms.

• This unit is the This unit is the picometer, pm.picometer, pm.

Chapter 3


Lesson StarterLesson Starter• Imagine that your semester grade depends 60% on Imagine that your semester grade depends 60% on

exam scores and 40% on laboratory explorations.exam scores and 40% on laboratory explorations.

• Your exam scores would count more heavily Your exam scores would count more heavily toward your final grade.toward your final grade.

• In this section, you will learn that the atomic mass In this section, you will learn that the atomic mass of an element is a weighted average of the masses of an element is a weighted average of the masses of the naturally occurring isotopes of that of the naturally occurring isotopes of that element.element.

Chapter 3


ObjectivesObjectives• ExplainExplain what isotopes are. what isotopes are.

• DefineDefine atomic numberatomic number and and mass number,mass number, and and describedescribe how they apply to isotopes. how they apply to isotopes.

• Given the identity of a nuclide, Given the identity of a nuclide, determinedetermine its its number of protons, neutrons, and electrons.number of protons, neutrons, and electrons.

• Define Define mole, Avogadro’s number,mole, Avogadro’s number, and and molar mass,molar mass, and state how all three are related.and state how all three are related.

Chapter 3

Solve problems involving mass in grams, amount in moles, and number of atoms of an element.


Atomic NumberAtomic Number• Atoms of different elements have different Atoms of different elements have different

numbers of protons.numbers of protons.

• Atoms of the same element all have the same Atoms of the same element all have the same number of protons.number of protons.

• TheThe atomic number atomic number (Z) of an element is the (Z) of an element is the number of protons of each atom of that number of protons of each atom of that element.element.

Chapter 3

Visual Concepts

Atomic NumberAtomic Number

Chapter 3


IsotopesIsotopes• IsotopesIsotopes are atoms of the same element that are atoms of the same element that

have different masses.have different masses.

• The isotopes of a particular element all have The isotopes of a particular element all have the same number of protons and electrons but the same number of protons and electrons but different numbers of neutrons.different numbers of neutrons.

• Most of the elements consist of mixtures of Most of the elements consist of mixtures of isotopes.isotopes.

Chapter 3


Mass NumberMass Number• The The mass numbermass number is the total number of is the total number of

protons and neutrons that make up the protons and neutrons that make up the nucleus of an isotope.nucleus of an isotope.

Chapter 3

Visual Concepts

Mass NumberMass NumberChapter 3


Designating Designating IsotopesIsotopes

• Hyphen notation:Hyphen notation: The mass number is The mass number is written with a hyphen after the name of written with a hyphen after the name of the element.the element.

uranium-235uranium-235

• Nuclear symbol: Nuclear symbol: The superscript indicates The superscript indicates the mass number and the subscript the mass number and the subscript indicates the atomic number.indicates the atomic number.

235 92 U

Chapter 3


• The number of neutrons is found by The number of neutrons is found by subtracting the atomic number from the subtracting the atomic number from the mass number.mass number.

mass number mass number atomic number = number of neutrons atomic number = number of neutrons

235 (protons + neutrons) 235 (protons + neutrons) 92 protons = 143 neutrons 92 protons = 143 neutrons

• NuclideNuclide is a general term for a specific is a general term for a specific isotope of an element.isotope of an element.

Chapter 3

Visual Concepts

Isotopes and Isotopes and NuclidesNuclides

Chapter 3


Sample Problem ASample Problem A

How many protons, electrons, and How many protons, electrons, and neutrons are there in an atom of chlorine-neutrons are there in an atom of chlorine-37?37?

Chapter 3


Given:Given: name and mass number of name and mass number of chlorine-37chlorine-37

Chapter 3

Solution: atomic number = number of protons = number of electronsmass number = number of neutrons + number of protons

Unknown: numbers of protons, electrons, and neutrons

Sample Problem A Solution


mass number of chlorine-37 mass number of chlorine-37 atomic atomic number of chlorine = number of neutrons number of chlorine = number of neutrons in chlorine-37in chlorine-37

Chapter 3

An atom of chlorine-37 is made up of 17 electrons, 17 protons, and 20 neutrons.

mass number atomic number = 37 (protons plus neutrons) 17 protons = 20 neutrons

Sample Problem A Solution, continued


Relative Atomic Relative Atomic MassesMasses• The standard used by scientists to compare The standard used by scientists to compare

units of atomic mass is the carbon-12 atom, units of atomic mass is the carbon-12 atom, which has been arbitrarily assigned a mass which has been arbitrarily assigned a mass of exactly 12 atomic mass units, or 12 amu.of exactly 12 atomic mass units, or 12 amu.

• One One atomic mass unit,atomic mass unit, or 1 or 1 amu,amu, is exactly is exactly 1/12 the mass of a carbon-12 atom.1/12 the mass of a carbon-12 atom.

• The atomic mass of any atom is determined The atomic mass of any atom is determined by comparing it with the mass of the by comparing it with the mass of the carbon-12 atom.carbon-12 atom.

Chapter 3


Average Atomic Masses of Average Atomic Masses of ElementsElements

• Average atomic massAverage atomic mass is the weighted is the weighted average of the atomic masses of the average of the atomic masses of the naturally occurring isotopes of an element.naturally occurring isotopes of an element.

Calculating Average Atomic MassCalculating Average Atomic Mass

• The average atomic mass of an element The average atomic mass of an element depends on both the mass and the relative depends on both the mass and the relative abundance of each of the element’s abundance of each of the element’s isotopes.isotopes.


Calculating Average Atomic Mass, Calculating Average Atomic Mass, continuedcontinued

Chapter 3

Copper consists of 69.15% copper-63, which has an atomic mass of 62.929 601 amu, and 30.85% copper-65, which has an atomic mass of 64.927 794 amu.

The average atomic mass of copper can be calculated by multiplying the atomic mass of each isotope by its relative abundance (expressed in decimal form) and adding the results.


• (0.6915 (0.6915 62.929 601 amu) + (0.3085 62.929 601 amu) + (0.3085 64.927 794 amu) = 63.55 amu 64.927 794 amu) = 63.55 amu

Chapter 3

Calculating Average Atomic Mass, continued

The calculated average atomic mass of naturally occurring copper is 63.55 amu.


Relating Mass to Relating Mass to Numbers of AtomsNumbers of Atoms

The MoleThe Mole

Chapter 3

Avogadro’s number—6.022 1415 1023—is the number of particles in exactly one mole of a pure substance.

Avogadro’s Number

A mole (abbreviated mol) is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.

The mole is the SI unit for amount of substance.


Molar MassMolar Mass

Chapter 3

The molar mass of an element is numerically equal to the atomic mass of the element in atomic mass units.

Molar mass is usually written in units of g/mol.

The mass of one mole of a pure substance is called the molar mass of that substance.


• Chemists use molar mass as a conversion Chemists use molar mass as a conversion factor in chemical calculations.factor in chemical calculations.

4.00 g He2.00 mol He = 8.00 g He

1 mol He×

Chapter 3

To find how many grams of helium there are in two moles of helium, multiply by the molar mass.

For example, the molar mass of helium is 4.00 g He/mol He.

Gram/Mole Conversions


• Avogadro’s number can be used to find Avogadro’s number can be used to find the number of atoms of an element from the number of atoms of an element from the amount in moles or to find the the amount in moles or to find the amount of an element in moles from the amount of an element in moles from the number of atoms.number of atoms.

Chapter 3

In these calculations, Avogadro’s number is expressed in units of atoms per mole.

Conversions with Avogadro’s Number

Solving Mole Solving Mole ProblemsProblems

Section 3 Counting AtomsChapter 3

Determining the Mass Determining the Mass from the Amount in Molesfrom the Amount in Moles

Section 3 Counting AtomsChapter 3


Sample Problem BSample Problem B

What is the mass in grams of 3.50 mol What is the mass in grams of 3.50 mol of the element copper, Cu?of the element copper, Cu?

Chapter 3


Sample Problem B SolutionSample Problem B Solution

Given:Given: 3.50 mol Cu 3.50 mol Cu

Unknown:Unknown: mass of Cu in grams mass of Cu in grams

Solution:Solution: the mass of an element in the mass of an element in grams can be calculated by multiplying grams can be calculated by multiplying the amount of the element in moles by the amount of the element in moles by the element’s molar mass.the element’s molar mass. moles Cu ×

grams Cumoles Cu

= grams Cu

Chapter 3


Sample Problem B Solution, Sample Problem B Solution, continuedcontinued

The molar mass of copper from the The molar mass of copper from the periodic table is rounded to 63.55 g/mol.periodic table is rounded to 63.55 g/mol.

3.50 mol Cu ×

63.55 g Cu1 mol Cu

= 222 g Cu

Chapter 3


Sample Problem CSample Problem C

A chemist produced 11.9 g of aluminum, A chemist produced 11.9 g of aluminum, Al. How many moles of aluminum were Al. How many moles of aluminum were produced?produced?

Chapter 3


Sample Problem C SolutionSample Problem C Solution

Given:Given: 11.9 g Al 11.9 g Al

Unknown:Unknown: amount of Al in moles amount of Al in moles

Solution:Solution:×

moles Algrams Al = moles Al

grams Al

1 mol Al11.9 g Al =

26.0.441

98 g Al mol Al×

Chapter 3

The molar mass of aluminum from the periodic table is rounded to 26.98 g/mol.


Sample Problem DSample Problem D

How many moles of silver, Ag, are in 3.01 How many moles of silver, Ag, are in 3.01 10 102323 atoms of silver? atoms of silver?

Chapter 3


Sample Problem D SolutionSample Problem D Solution

Given:Given: 3.01 3.01 10 102323 atoms of Ag atoms of Ag

Unknown:Unknown: amount of Ag in moles amount of Ag in moles

Solution:Solution:×

moles AgAg atoms = moles Ag

Avogadro's number of Ag atoms

2323

1 mol Ag3.01 10 Ag atoms

6.022 10 Ag at

0.500

=

m

oms

ol Ag

× ××

Chapter 3


Sample Problem ESample Problem E

What is the mass in grams of 1.20 What is the mass in grams of 1.20 10 1088 atoms of copper, Cu?atoms of copper, Cu?

Chapter 3


Sample Problem E SolutionSample Problem E Solution

Given:Given: 1.20 1.20 10 1088 atoms of Cu atoms of Cu

Unknown:Unknown: mass of Cu in grams mass of Cu in grams

Solution:Solution:

The molar mass of copper from the periodic table is The molar mass of copper from the periodic table is rounded to 63.55 g/mol.rounded to 63.55 g/mol.

14

823

1 mol Cu 63.55 g Cu1.20 10 Cu atoms =

6.022 10 Cu atoms 1 mol Cu

1. 27 10 Cu g ×

× × ××

–

Relating Mass to Numbers of Atoms, continued

Chapter 3

Copyright © by Holt, Rinehart and Winston. All rights reserved.

ResourcesChapter menu

End of Chapter 3 Show

Standardized Test Preparation

Multiple ChoiceMultiple Choice1.1. A chemical compound always has the A chemical compound always has the same elements in the same proportions by same elements in the same proportions by mass regardless of the source of the mass regardless of the source of the compound. This is a statement ofcompound. This is a statement of

A.A. the law of multiple proportions.the law of multiple proportions.

B.B. the law of isotopes.the law of isotopes.

C.C. the law of definite proportions.the law of definite proportions.

D.D. the law of conservation of mass.the law of conservation of mass.

Chapter 3


Multiple ChoiceMultiple Choice

Chapter 3

2. An important result of Rutherford’s experiments with gold foil was to establish that

A. atoms have mass.

B. electrons have a negative charge.

C. neutrons are uncharged particles.

D. the atom is mostly empty space.


Multiple ChoiceMultiple Choice3.3. Which subatomic particle has a Which subatomic particle has a charge of +1?charge of +1?

A.A. electronelectron

B.B. neutronneutron

C.C. protonproton

D.D. mesonmeson

Chapter 3


Multiple ChoiceMultiple Choice4.4. Which particle has the least Which particle has the least mass?mass?

A.A. electronelectron

B.B. neutronneutron

C.C. protonproton

D.D. All have the same mass.All have the same mass.

Chapter 3


Multiple ChoiceMultiple Choice

Chapter 3

5. Cathode rays are composed of

A. alpha particles.

B. electrons.

C. protons.

D. neutrons.


Multiple ChoiceMultiple Choice6.6. The atomic number of an element is The atomic number of an element is the same as the number ofthe same as the number of

A.A. protons.protons.

B.B. neutrons.neutrons.

C.C. protons + electrons.protons + electrons.

D.D. protons + neutrons.protons + neutrons.

Chapter 3


Multiple ChoiceMultiple Choice7.7. How many neutrons are present in How many neutrons are present in an atom of tin that has an atomic number an atom of tin that has an atomic number of 50 and a mass number of 119?of 50 and a mass number of 119?

A.A. 5050

B.B. 6969

C.C. 119119

D.D. 169169

Chapter 3


Multiple ChoiceMultiple Choice8.8. What is the mass of 1.50 mol of What is the mass of 1.50 mol of sodium, Na?sodium, Na?

A.A. 0.652 g0.652 g

B.B. 0.478 g0.478 g

C.C. 11.0 g11.0 g

D.D. 34.5 g34.5 g

Chapter 3


Multiple ChoiceMultiple Choice9.9. How many moles of carbon are in a How many moles of carbon are in a 28.0 g sample?28.0 g sample?

• A.A. 336 mol336 mol

• B.B. 72.0 mol72.0 mol

• C.C. 2.33 mol2.33 mol

• D.D. 0.500 mol0.500 mol

Chapter 3


Short AnswerShort Answer• 10. Which atom has more neutrons, 10. Which atom has more neutrons,

potassium-40 or argon-40?potassium-40 or argon-40?

Chapter 3


Short AnswerShort Answer• 11. What is the mass of 1.20 11. What is the mass of 1.20 10 102323

atoms of phosphorus?atoms of phosphorus?

Chapter 3


Extended ResponseExtended Response

Chapter 3

12. Cathode rays emitted by a piece of silver and a piece of copper illustrate identical properties. What is the significance of this observation?


Extended ResponseExtended Response• 13.13. A student believed that she had A student believed that she had

discovered a new element and named discovered a new element and named it mythium. Analysis found it it mythium. Analysis found it contained two isotopes. The contained two isotopes. The composition of the isotopes was composition of the isotopes was 19.9% of atomic mass 10.013 and 19.9% of atomic mass 10.013 and 80.1% of atomic mass 11.009. What is 80.1% of atomic mass 11.009. What is the average atomic mass, and do you the average atomic mass, and do you think mythium was a new element?think mythium was a new element?

Chapter 3

Important factsImportant facts



•Here is a Bohr model of a Here is a Bohr model of a carbon atom.carbon atom.


Beryllium Atom Fluorine Atom Carbon Atom


–All matter is made up of All matter is made up of extremely small particles called extremely small particles called atoms. These particles are too atoms. These particles are too small to be seen even with a small to be seen even with a microscope.microscope.

–Science is theoretical and Science is theoretical and dynamic. Models and theories dynamic. Models and theories are continually being revised, are continually being revised, refined, or replaced with new refined, or replaced with new models and theories.models and theories.


–Atomic number is the Atomic number is the number of protons in the number of protons in the nucleus of an atom.nucleus of an atom.

–Mass number is the mass Mass number is the mass of an individual atom.of an individual atom.


element chemical symbol

atomic number

# of protons

# of electrons

# of neutrons

mass number

atomic weight

beryllium Be 4 4 4 5 9 9.001

fluorine F 9 9 9 10 19 18.9

Carbon C 6 6 6 6 12 12.011

chlorine Cl 17 17 17 18 35 35.45

lead 126

potassium 19 39

tin 70

tungsten 184 183.85

29 36

gold 118


– If you know the atomic number If you know the atomic number of an element, what other of an element, what other information can you figure out information can you figure out about the atoms of that about the atoms of that element?element?

– If you know the atomic number If you know the atomic number of an element, can you figure out of an element, can you figure out how many neutrons an atom of how many neutrons an atom of that element has?. that element has?.


–Mass number is the number of Mass number is the number of protons plus the number of protons plus the number of neutrons.neutrons.

–Atomic mass is the “weight” Atomic mass is the “weight” or mass of a single atom.or mass of a single atom.

–Atomic weight is the decimal Atomic weight is the decimal number on the periodic table. number on the periodic table.


PracticePracticeUse your periodic table to Use your periodic table to identify the following elements:identify the following elements:

•a) Atomic number 10a) Atomic number 10

•b) Has five electronsb) Has five electrons

•c) Atomic mass of 15.99c) Atomic mass of 15.99


–Each successive element has one Each successive element has one more proton than the element more proton than the element preceding it. preceding it.

–The atomic number is equal to The atomic number is equal to the number of protons.the number of protons.


–The number of electrons is equal The number of electrons is equal to the number of protons (as to the number of protons (as long as the atom is neutral).long as the atom is neutral).

–The mass number is equal to the The mass number is equal to the number of protons plus the number of protons plus the number of neutrons (most of the number of neutrons (most of the mass is found in the nucleus).mass is found in the nucleus).

Documents

Table of Contents Chapter 3 Atoms: The Building Blocks of Matter Section 1 The Atom: From Philosophical Idea to Scientific Theory Section 2 The Structure