Atomic Theory: Dalton’s Atomic Theory The Nuclear Model of ...facweb.northseattle.edu/jowens/139/PDFwordppt/chapter5.pdf · Atomic Theory: The Nuclear Model of the Atom Chapter

1

Atomic Theory:

The Nuclear Modelof the Atom

Chapter 5

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007

Brooks/Cole, a part of the Thomson Corporation.

Section 5.1

Dalton’s Atomic Theory



Identify the main features of Dalton’s atomic

theory.

Goal 1



Precursors to John Dalton’s atomic theory

Law of Definite Composition

The percentage by mass of the elementsin a compound is always the same

Law of Conservation of Mass

In a chemical change, mass is converved



Dalton’s Atomic Theory (1808)

Each element is made up of tiny,individual particles called atoms.

Atoms are indivisible;

they cannot be created or destroyed

All atoms of each element

are identical in every respect.

Atoms of one element are different

from atoms of any other element.

Atoms of one element may combine with atoms of other

elements, usually in the ratio of small, whole numbers,

to form chemical compoundsPresentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007




2

Law of Multiple Proportions

When two elements combine to form more than one

compound, the different weights of one element that

combine with the same weight of the other element are in a simple ratio of whole numbers.



Section 5.2

Subatomic Particles



Identify the three major subatomic particles by

charge and approximate atomic mass, expressed

in atomic mass units.

Goal 2



An atom contains smaller partsknown as subatomic particles.

Electron

1– charge, 0.000549 amu

Proton

1+ charge, 1.00728 amu

Neutronno charge, 1.00867 amu





Section 5.3

The Nuclear Atom



3

Describe and/or interpret the Rutherford

scattering experiment and the nuclear model of

the atom.

Goal 3







The Nuclear Model of the Atom

Every atom contains an extremelysmall, extremely dense nucleus.

All of the positive charge and nearly all of the mass of

an atom are concentrated in the nucleus.

The nucleus is surrounded by a much

larger volume of nearly empty spacethat makes up the rest of the atom.

The space outside the nucleus is very thinly populated by electrons, the total charge of which exactly balances

the positive charge of the nucleus.Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007




The diameter of an atom is approximately 100,000

times the diameter of the

nucleus.

If the nucleus was the size of a pea,

there would be a 1 km distance

from it to its nearest neighbor

1 km



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Section 5.4

Isotopes



Explain what isotopes of an element are and how

they differ from each other.

Goal 4



For an isotope of any element whose chemical

symbol is known, given one of the following, state

the other two: (a) nuclear symbol, (b) number of

protons and neutrons, (c) atomic number and mass number.

Goal 5



Identify the features of Dalton’s atomic theory

that are no longer considered valid, and explain

why.

Goal 6



Every atom of a particular elementhas the same number of protons.

The number of protons in an atom of anelement is the atomic number, Z

Atoms are electrically neutral

Protons have a 1+ charge

Electrons have a 1– charge

The number of electrons in an atom therefore

must be equal to the number of protons



All atoms of an element are not identicalSome have more mass than others

Since the number of protons and electrons

in an atom of an element are fixed,there must be variation in the number

of neutrons that causes this difference in mass

Atoms of the same element that have different

masses—different numbers of neutrons—are called isotopes



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An isotope is identified by its mass number, A

Mass number = A =

Total number of protons + neutrons

Mass number = # of protons + # of neutrons

A = Z + # of neutrons



Name of an Isotope

Elemental name–Mass number

Example:

A carbon atom with 6 protons and 6 neutrons

Mass number: 6 + 6 = 12

Name: carbon-12

What is the name of the carbon

isotope with 7 neutrons?

carbon-13



Symbol of an Isotope

Known as a nuclear symbol

# of protons + # of neutrons

# of protons Sy

mass number

atomic numberSy

A

Z Sy

Example:

What are the nuclear symbols for

carbon-12 and carbon-13?

12

6C

13

6C



Section 5.5

Atomic Mass



Define and use the atomic mass unit (amu).

Goal 7



Given the relative abundances of the natural

isotopes of an element and the atomic mass of

each isotope, calculate the atomic mass of the element.

Goal 8



6

Masses of atoms are expressed inatomic mass units, amu

1 amu the mass of one carbon atom1

12

12 amu the mass of one carbon atom

C atom: 6 p+, 6 n, 6 e–

Since the mass of a p+ and a n are about the

same, and since the mass of an e– is about 0,12 amu = mass of (6 + 6) (p+ + n)

12 amu = mass of 12 nuclear subatomic particles

1 amu = mass of 1 nuclear subatomic particle



1 amu = 1.66 x 10–24 g





Mass Spectrum of Neon Atomic Mass(of an element):

The average mass of all atoms of an

element as they occur in nature.

Chlorine has two natural isotopes:

75.78% is chlorine-35 at 34.968852721 amu

24.22% is chlorine-37 at 36.96590262 amu

What is the atomic mass of chlorine?

0.7578 x 34.968852721 amu =

0.2422 x 36.96590262 amu =

26.50 amu

8.953 amu

35.45 amuPresentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007


Section 5.6

The Periodic Table



Distinguish between groups and periods in the

periodic table and identify them by number.

Goal 9



7

Given the atomic number of an element, use a

periodic table to find the symbol and atomic mass

of that element, and identify the period and group in which it is found.

Goal 10



When elements are arranged according

to their atomic masses, certain properties

repeat at periodic intervals(Mendeleev and Meyer, 1869)

Periodic Tableof the Elements

A table that arranges the elements in

order of atomic number with elements

with similar properties in the same column



Mendeleev had blank spaces in his periodic table.

He averaged the properties of the surrounding elements to predict properties of as-yet

undiscovered elements.







PeriodsHorizontal rows in the periodic table

Numbered 1–7, top to bottom

(numbers usually not printed)

Groups (or Chemical Families)Vertical columns in the periodic table

U.S. numbering: A groups and B groups

IUPAC numbering: 1-18, left to right



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Main group elementsElements in the U.S. A-groups

Transition elementsElements in the U.S. B-groups

MetalsElements on the left of the stair-step line

NonmetalsElements on the right of the stair-step line



Section 5.7

Elemental Symbols and

the Periodic Table



Given the name or the symbol of an element in

Figure 5.9, write the other.

Goal 11





aluminum

argon

bariumberyllium

boron

Al

ArBa

Be

B

BrCa

C

ClCr

bromine

calciumcarbon

chlorinechromium



cobalt

copperfluorine

helium

hydrogen

CoCu

FHe

H

I

FeKr

Pb

Li

iodineiron

krypton

lead

lithium



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magnesium

manganesemercury

neon

nickel

Mg

Mn

Hg

Ne

Ni

N

OP

K

Si

nitrogenoxygen

phosphorus

potassium

silicon



silver

sodiumsulfur

tin

zinc

Ag

Na

S

Sn

Zn



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Atomic Theory: Dalton’s Atomic Theory The Nuclear Model of ...facweb.northseattle.edu/jowens/139/PDFwordppt/chapter5.pdf · Atomic Theory: The Nuclear Model of the Atom Chapter