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Chapter 5 Atomic Theory: The Nuclear Model of the Atom. 5.1 Dalton ’ s Atomic Theory. 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.

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Chapter 5 atomic theory the nuclear model of the atom

Chapter 5Atomic Theory:The Nuclear Model of the Atom

5 1 dalton s atomic theory
5.1 Dalton’s Atomic Theory

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 compounds.

5 1 dalton s atomic theory1
5.1 Dalton’s Atomic Theory

The atoms are neither created nor destroyed in chemical reactions, but simply arranged differently to form the products.

5 1 dalton s atomic theory2

Law of Multiple Proportions

When two elements combine to form more than one compound, the different masses of one element that combine with the same mass of the other element are in a simple ratio of whole numbers.

5.1 Dalton’s Atomic Theory

Subatomic particles
Subatomic Particles

Goal 3

Identify the three major subatomic particles by symbol, charge, and approximate atomic mass, expressed in atomic mass units.

5 2 subatomic particles
5.2 Subatomic Particles


Symbol: e or e–

Fundamental charge: 1–

Mass (g): 9 × 10–28 g

Mass (atomic mass unit): 0.000549 u

Location: Outside nucleus

Discovered: 1897 by Thomson

Subatomic particles1
Subatomic Particles


Symbol: p or p+

Fundamental charge: 1+

Mass (g): 1.673  10–24 g

Mass (u): 1.00728 u

Location: Inside nucleus

Discovered: 1919 by Rutherford

Subatomic particles2
Subatomic Particles


Symbol: n or n0

Fundamental charge: 0

Mass (g): 1.675  10–24 g

Mass (u): 1.00867 u

Location: Inside nucleus

Discovered: 1932 by Chadwick

5 3 the nuclear atom
5.3 The Nuclear Atom

5 3 the nuclear atom1
5.3 The Nuclear Atom

The Nuclear Model of the Atom

  • An electron with a mass of 1/1837 u could not have deflected an alpha particle with a mass of 4 u.

  • Rutherford concluded that each gold atom contained a positively charged mass that occupied a tiny volume. He called this mass the nucleus.

5 3 the nuclear atom2
5.3 The Nuclear Atom

The Nuclear Model of the Atom

  • Every atom contains an extremely small, 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 space that 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.

5 3 the nuclear atom3

TThediameter of an atom is approximately 10,000 times the diameter of its nucleus.

5.3 The Nuclear Atom

5 3 the nuclear atom4
5.3 The Nuclear Atom

Planetary Model of the Atom (1911)

Electrons travel in circular orbits around the nucleus,

much like planets move in orbits around the sun.

5 4 isotopes
5.4 Isotopes

Every atom of any particular element

has the same number of protons, which is called the atomic number, Z.

Atoms are electrically neutral, the number of electrons in an atom therefore must be equal to the number of protons.

5 4 isotopes1
5.4 Isotopes

All atoms of any particular element are not identical; the number of neutrons may be different.

Atoms of the same element that have different numbers of neutrons—different masses—are called isotopes.

5 4 isotopes2
5.4 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 + N

5 4 isotopes3
5.4 Isotopes

Name of an Isotope

Elemental name–Mass number


What is the name of the carbon atom with 6 protons and 6 neutrons?

Mass number = 6 + 6 =12, so the name is carbon-12

What is the name of the carbon isotope with 7 neutrons?

Mass number is 6 + 7 = 13, so the name is carbon-13

5 4 isotopes4
5.4 Isotopes

Symbol of an Isotope

Known as a nuclear symbol


What are the nuclear symbols for carbon-12 and carbon-13?

5 5 atomic mass
5.5 Atomic Mass

Masses of atoms are expressed in

atomic mass units, u.

The u is defined as

1 u  1/12 the mass of one carbon-12 atom

1 u  mass of 1 nuclear subatomic particle

5 5 atomic mass1
5.5 Atomic Mass

Percentage Abundance of Some Natural Isotopes

SymbolMass (u)Percent

1H 1.0078250321 99.9885

2H 2.0141017780 0.0115

12C 12 (exactly) 98.93

13C 13.0033548378 1.07

39K 38.9637069 93.2581

40K 39.96399867 0.0117

41K 40.96182597 6.7302

5 5 atomic mass2

This is the mass spectrum of neon.

The relative abundance plotted on the y-axis is the percentage of each isotope found in a natural sample of the pure element.

The mass-to-charge ratio, m/z, is plotted on the x-axis. Since this plot shows 1+ ions only, m/z is the mass of the isotope, expressed in u.

5.5 Atomic Mass

5 5 atomic mass3
5.5 Atomic Mass

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 u and 24.22% is chlorine-37 at 36.96590262 u. What is the atomic mass of chlorine?


0.7578 ×34.968852721 u = 26.50 u

0.2422 ×36.96590262 u = 8.95 3 u

35.45 u

5 6 the periodic table
5.6 The Periodic Table

Periodic Table of the Elements

A table that arranges the elements in order

of increasing atomic number.

Elements with similar properties appear in the same column.

5 6 the periodic table1
5.6 The Periodic Table

5 6 the periodic table2
5.6 The Periodic Table


Horizontal 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

5 6 the periodic table3
5.6 The Periodic Table

Main group elements

(sometimes called representative elements)

Elements in the U.S. A-groups

Transition elements

Elements in the U.S. B-groups


Elements on the left of the stair-step line


Elements on the right of the stair-step line

5 8 elemental symbols
5.8 Elemental Symbols

Memorize the 35 name–symbol pairs given in Fig. 5.8.

Look at the location of each element in the periodic table while you work on memorization—it will help you remember the names and symbols.

Whenever a chemical symbol has two letters,

the first letter is always capitalized and

the second letter is always written in lowercase.


Homework for chapter 5:

17, 19, 21, 27,29, 31, 39, 41, 54