Tài liệu Types of Atomic & Molecular Bonds pptx

Types of Atomic &
Molecular Bonds
Types of Atomic &
Molecular Bonds
Types of Atomic & Molecular
Bonds
Types of Atomic & Molecular
Bonds
Objectives of the class
Develop a sense of history of scientific thinking
Explain the types of bonds
You should be able to have develop a “feeling” for the
mechanical properties based on the type of bond
Long Tradition in ScienceLong Tradition in Science
Greek philosopher Leucippus used the word
atom, which means indivisible (400 BC)
Lots of work done by the alchemists
Lavoisier: chemical reaction leads to no net
loss or gain of matter.
Dalton: concept of atomic mass (1808)
Mendelev: periodic table of elements (1869)
Moseley: showed that the number of electrons
= number of protons (atomic number)
Discovery of X-raysDiscovery of X-rays
Wilhelm Conrad Roentgen
first Nobel prize in physics (1901)
Long Tradition in Science
(cont.)
Long Tradition in Science
(cont.)
Ruterford: experiments with alpha

particle (1907-11)
Max Planck: quanta (1900)
Louis de Broglie: all matter has both
wave and particle properties
(1923).
Types of Atomic & Molecular
Bonds
Types of Atomic & Molecular
Bonds
Primary Atomic Bonds
Ionic Bonds
Covalent Bonds
Metallic Bonds
Secondary Atomic & Molecular
Bonds
Permanent Dipole Bonds
Fluctuating Dipole Bonds
IMPORTANT!!!
Ionic BondingIonic Bonding
Large interatomic forces are created by the
“coulombic” effect produced by positively
and negatively charged ions.
Ionic bonds are “nondirectional”.
The “cation” has a + charge & the “anion” has
the - charge.
The cation is much smaller than the
anion.
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17
Historical NoteHistorical Note

Greek philosopher Empedocles (500
BC) suggested that chemical
changes are caused by an
emotional likes and dislikes.
The love between two substances
will make them unite and form a
third substance. On the other
hand, if the substances start to had
each other they will decompose.
Force vs. Separation DistanceForce vs. Separation Distance
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Energy vs. Separation DistanceEnergy vs. Separation Distance
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F

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Modulus of ElasticityModulus of Elasticity
Effect of temperatureEffect of temperature
Ionic Bonding in SolidsIonic Bonding in Solids
Because the ionic bond is
nondirectional the ions pack
together in a solid in ways
which are governed by their
relative sizes.
Another important factor is that
the ions must be arranged so
that their is local charge
neutrality. [Note the structure
of NaCl.].
Covalent BondingCovalent Bonding
Large interatomic forces are created by the sharing of
electrons to form directional bonds.
The atoms have small differences in electronegativity
& close to each other in the periodic table.
The atoms share their outer s and p electrons so that
each atom attains the noble-gas electron
configuration.
RepresentationsRepresentations
discrete cloud
Covalent Bonding in CarbonCovalent Bonding in Carbon
A carbon atom can form form sp

3
orbitals directed symmetrically
toward the corners of a
tetrahedron. [Note the examples
below.]
Diamond
Metallic BondingMetallic Bonding
Large interatomic forces are created by the
sharing of electrons in a delocalized
manner to form strong nondirectional
bonding.
Metalic BondMetalic Bond
It is convenient for many purposes to regard an atom
in a metal as having a definite size, which may be
defined by the distance between its center and that
of its neighbor.
This distance is that at which the various forces acting
on the atom are in equilibrium.
In a metal, the forces can be considered as
– (a) the attractive forces between electrons &
positive ions,
– (b) the repulsion between the complete electron
shells of the positive ions, &
– (c) the repulsion between the positive ions as a
result of their similar positive charges.
Secondary Atomic & Molecular Bonds
[Van der Waals Bonds]
Secondary Atomic & Molecular Bonds
[Van der Waals Bonds]
Permanent Dipole Bonds

– Weak intermolecular bonds are formed between molecules
which possess permanent dipoles.
– A dipole exists in a molecule if there is asymmetry in its
electron density distribution.
Fluctuating Dipole Bonds
– Weak electric dipole bonding can take place among atoms
due to an instantaneous asymmetrical distribution of
electron densities around their nuclei.
– This type of bonding is termed fluctuation since the
electron density is continuously changing.
Polar dipolePolar dipole
Van der Walls bondsVan der Walls bonds
The Hard Sphere ModelThe Hard Sphere Model
This approach can be called the "hard sphere" model
of an atom.
The radius of an atom (or ion) determined for a
particular crystal structure is not a real
characteristic of that atom, because when the same
atom appears in different crystal structure it displays
different radii.
The radius of an atom (or ion) can be determined for a
particular metal by using the dimensions of the unit
cell of the crystal structure it forms.