Atomic Theory: The Nuclear Model of the Atom Chapter 5 Presentation Slides to Accompany...

Atomic Theory:The Nuclear Model

of 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 CompositionThe percentage by mass of the elements

in a compound is always the same

Law of Conservation of MassIn 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 elementare identical in every respect.

Atoms of one element are differentfrom 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

Brooks/Cole, a part of the Thomson Corporation.


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.

Electron1– charge, 0.000549 amu

Proton1+ charge, 1.00728 amu

Neutronno charge, 1.00867 amu



Section 5.3

The Nuclear Atom


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 muchlarger 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 distancefrom it to its nearest neighbor

1 km


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 neutralProtons have a 1+ chargeElectrons have a 1– charge

The number of electrons in an atom thereforemust 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 electronsin an atom of an element are fixed,

there must be variation in the numberof neutrons that causes this difference in mass

Atoms of the same element that have different masses—different numbers of neutrons—

are called isotopes


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 = 12Name: carbon-12

What is the name of the carbonisotope 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

AZ Sy

Example:What are the nuclear symbols for

carbon-12 and carbon-13?126 C

136 C


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


Masses of atoms are expressed inatomic mass units, amu

1 amuthe mass of one carbon atom

1

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



Mass Spectrum of Neon

Atomic Mass(of an element):

The average mass of all atoms of anelement as they occur in nature.

Chlorine has two natural isotopes:75.78% is chlorine-35 at 34.968852721 amu24.22% 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


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 accordingto their atomic masses, certain properties

repeat at periodic intervals(Mendeleev and Meyer, 1869)

Periodic Tableof the Elements

A table that arranges the elements inorder 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 groupsIUPAC numbering: 1-18, left to right


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



aluminumargonbariumberylliumboron

AlArBaBeB

BrCaCClCr

brominecalciumcarbonchlorine

chromium


cobaltcopperfluorineheliumhydrogen

CoCuF

HeH

IFeKrPbLi

iodineiron

kryptonlead

lithium


magnesiummanganesemercuryneonnickel

MgMnHgNeNi

NOPKSi

nitrogenoxygen

phosphoruspotassium

silicon


silversodiumsulfurtinzinc

AgNaSSnZn


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