chapter 2 - C h a p t e r 2 Atomic Structure and...

C h a p t e r 2 / Atomic Structure and Interatomic Bonding C h a p t e r 2
Atomic Structure and Interatomic Bonding
Why Study Atomic Structure and Interatomic Bonding?
important
properties of
materials
depend on
atomic arrangements
This chapter, considers several fundamental and
important concepts ,
atomic structure , electron configurations in atoms
and the periodic table , and the various types of
primary and secondary interatomic bonds that hold
together the atoms comprising a solid.
2.1 Introduction

C h a p t e r 2 / Atomic Structure and Interatomic Bonding
T his micrograph, which
represents the surface of a
gold specimen , was taken
with a sophisticated atomic
force microscope (AFM) .
Individual
atoms for this (111)
crystallographic surface
plane are resolved. Also
note the dimensional scale
(in the nanometer range ) below
the micrograph.

C h a p t e r 2 / Atomic Structure and Interatomic Bonding
2.2 Fundamental Concepts
atom
nucleus
electrons
protons
neutrons
Electrically charged
1.60 × 10
-19
C
1.67 × 10
-27
kg
9.11 × 10
-31
kg
the number of protons
characterize Each
chemical element
the atomic number ( Z ):
For a chemical element, the
number of protons within
the atomic nucleus.
=
the number of electrons
(for an electrically neutral
or complete atom)
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C h a p t e r 2 / Atomic Structure and Interatomic Bonding
The atomic number ranges in integral units from 1 for
hydrogen to 92 for uranium,
Isotopes
: Atoms of the same element that have different atomic
masses. the
number of neutrons ( N )
may be variable.
The
atomic mass ( A )
of a specific atom may be expressed as
the sum of the masses of protons and neutrons within the nucleus.
The
atomic weight ( A )
The weighted average of the atomic
masses of an atom’s naturally occurring isotopes.
The
atomic mass unit (amu):
A measure of atomic mass; one
twelfth of the mass of an atom of C
12
, carbon 12 (12C) ( A
12.00000).
A 2245 Z +
N
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C h a p t e r 2 / Atomic Structure and Interatomic Bonding
Mole:
The quantity of a substance corresponding to 6.023 × 10
23
atoms
or molecules.
1 amu/atom (or molecule) =1 g/mol
2.3 Electrons in Atoms
Atomic Models
Quantum mechanics. A branch of physics that deals with
atomic and subatomic systems; it allows only discrete values of
energy that are separated from one another. By contrast, for
classical mechanics, continuous energy values are permissible.
For example, the atomic weight of iron is 55.85 amu/atom, or 55.85
g/mol.
“A”
may be expressed in terms of atomic mass units (on an
atomic basis), or the mass per mole of atoms.
during the latter part of the nineteenth century
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C h a p t e r 2 / Atomic Structure and Interatomic Bonding
Bohr atomic model:
An early
atomic model, in which electrons
are assumed to revolve around the
nucleus in discrete orbitals .