Transcript Characteristics of Solids

CHARACTERISTICS OF SOLIDS
REVIEW
Element → One of over 118 types of pure
substances from which all material are formed
Atom → The smallest particle of an element
which all materials are formed.
THE PERIODIC TABLE
Is an organizational tool which can be used to predict
chemical and physical characteristics of elements.
It’s all in the familyFor example, if you are in
Family 18, the Noble Gases,
you and all the other
elements in that
group/family – Neon, Argon,
Krypton, Xenon and Radon
have similar characteristics.
Group
18
THE STAIRCASE
to the left of the
“staircase”
 Metals :
 about 75% of all the elements
 lustrous, malleable, ductile, conduct
heat and electricity
Nonmetals: on
the right
sides of the “staircase”
 dull, brittle, insulators
 Metalloids:
on the staircase
 also know as semi-metals
 often semi- conductors
 some properties of both metals &
nonmetals
HOW WAS THE TABLE FORMED?
Chemists discovered that as the quantity of
matter (atomic mass) increased,
characteristics tended to repeat themselves
in a predictable pattern. This was called
“Periodicity.”
When elements were placed in a table , those
with similar properties were placed in a
column, it produced vertical “Families.”
EXAMPLE OF PERIODICITY
Rows and Columns
Family = a vertical column (group) Period = the 7 horizontal row
These elements have similar
Periods represents the number
properties, reactivity and valence of layers of electrons in the
electrons.
atom.
COLUMN 18
 Noble gases
 very stable
 don’t want to form compounds or bonds
COLUMN 17
 halogens
 want one more electron
 most reactive nonmetals
 can take an electron from almost anyone
COLUMN 1
 alkali metals
 want to give away one electron
 most reactive metals
MODEL OF A LITHIUM ATOM
Composition of an Atom
3 types of Subatomic Particles
1. Electrons →
Is outside the nucleus and has a negative charge.
2. Protons →
A positively charged particle in the nucleus of a Atom.
It is ≈ the same mass as a Neutron
3. Neutron →
An uncharged particle located in the Nucleus of an
Atom. It is ≈ the same mass as a Proton.
Definitions
Nucleus →
The central portion of an atom – usually consisting
of protons and neutrons and contains almost all the
mass of the atom.
Atomic Number →
A number representing the number of protons in an
atom of an element.
Definitions
Mass →
The amount of material (stuff) in an object. Mass is
proportional to weight. Mass does not change when
gravity changes while weight does.
SUBATOMIC PARTICLES
Protons (p or +)
Neutrons (n)
Electrons (e-)
+1
No charge
-1
in nucleus
in nucleus
in shells around
nucleus
Mass
≈ 1 amu
≈ 1 amu
≈ 2000 x
smaller
“Job”
Determines identity
of element
Name
Charge
Location
Number
Atomic #
Supplies proper
mass to hold
nucleus together
Determines
bonding/ how it
reacts
Atomic mass –
atomic # =
# of neutrons
Same as #
of protons
EXAMPLE
Silver:
Symbol
Ag
Atomic Number of Silver is?
47
How many Protons does Ag have?
47
How many Electrons does Ag have?
47
How many Electron layers?
5
Definitions
Valence Electrons →
Electrons found in the outermost energy level or layer from
the nucleus. (These electrons are involved in bonding.)
Metal have a tendency to lose their valence electrons.
Nonmetals try to obtain valence electrons.
Finally we are done for today.
Finish Periodic Table/ Atom
Work Sheet
CRYSTAL STRUCTURES
Crystal →
An object with a regularly repeating arrangement of its
atoms.
Crystal Lattice →
The pattern that atomic particles form in a crystalline
solid.
Slip Plane →
A surface along which layers of atoms can slide.
14 different Crystalline Systems
14 different Crystalline Systems,
most metals fall into 3 categories
1) Body-Centered Cubic (BCC) →
A type of crystalline structure that is composed
of 8 particles forming a cube with a 9th particle in the
center of the cube.
14 different Crystalline Systems,
most metals fall into 3 categories
2) Face-Centered Cubic (FCC) →
A type of crystalline structure that is composed
of 8 particles forming a cube and 6 more particles that
are each centered in 1 of 6 faces of the cube.
14 different Crystalline Systems,
most metals fall into 3 categories
3) Hexagonal-Close Packed (HCP) →
A type of crystalline structure that is composed
of 17 particles which are as closely packed as
possible.
14 different Crystalline Systems,
most metals fall into 3 categories
Unit Cell →
The simplest and smallest arrangement of
atoms that can be repeated to form a particular
crystal.
MODEL OF CRYSTAL LAB
FORMATION OF SOLIDS
Allotropes →
Elements which occur in more than one form due to the
way their atoms are packed.
Iron @ room Temp → BCC
Iron above 910°C → FCC
Carbon can be a diamond or graphite depending
on how its atoms are packed.
CRYSTAL PACKING – LOOSELY
PACKED
Crystal Packing – More Densely Packed
Most metals
are close
packed - that
is, they fit as
many atoms as
possible into
the available
volume
GRAINS INFLUENCE PROPERTIES
Rapid cooling produces smaller grains
Slow cooling produces larger grains
Alloys of metals with more grains make the
material stronger
CRYSTAL GRAINS
“Crystal grains "are regions of regularity. At the grain
boundaries atoms have become misaligned. The more grain
boundaries there are (the smaller the individual crystal
grains), the harder and more brittle the metal becomes.
CRYSTAL SLIP PLANES IN METAL
To reshape metals, layers of atoms are forced
to slide over one another.
CRYSTAL STRUCTURE
 Which type of crystal structure allows a metal to be more
workable, one with many slip planes or one with fewer slip
planes?
 Ones with many Slip Planes
 Which type of crystal structure allows a metal slip planes
to be more workable, one that is closely packed or one that
is loosely packed?
 Ones that are closely packed.
Type of Crystal
Structure
Closely Packed?
Many Slip
Planes?
Workability
FCC
Yes
Yes
Highest
BCC
No
Yes
Medium
HCP
Yes
No
Lowest
BCC
FCC
Chromium
Iron (<910˚C)
Sodium
Tungsten
Aluminum
Calcium
Copper
Gold
Iron(>910˚C)
Lead
Nickel
Platinum
Silver
HCP
Cobalt
Magnesium
Titanium
Zinc
IRON WIRE LAB
METALLIC & NON-METALLIC
ELEMENTS
Metal →
Metals tend to lose electrons which changes them
from neutral atoms to positive ions.
Nonmetal →
Nonmetals gain electrons which changes them from
neutral atoms to negative ions.
METALLIC & NON-METALLIC
ELEMENTS
Ion →
An atom that has gained or lost at least one electron
and has a negative or positive charge.
Ionic Bond →
A bond resulting from the attractive force between
ions of opposite charges. (Metal & Non Metal bond to
form a compound). A very strong bond.
ELECTRON TRANSFER FROM A
METAL TO A NON METAL
Sodium lets Chlorine use its valance electron
TYPE OF BONDING
Metallic Bond →
The force that hold solid metal together.
METALLIC BONDING
All pure metals have metallic bonding and therefore exist as metallic
structures. Metallic bonding consists of a regular arrangement of
positive ion cores of the metals surrounded by a mobile delocalized sea of
electrons.
COVALENT BONDING →
A CHEMICAL ATTRACTION BETWEEN 2
NONMETALLIC ATOMS THAT ARE SHARING
ELECTRONS. (NON-METALS).
TYPE OF BONDING
Molecules→
When 2 or more nonmetals share electrons to form
covalent bonds.
Van der Waal Forces →
The weaker bonds that hold molecules to one
another.
Bonding
Non-metal
Atoms
Covalent
Bonds
Molecular
Compound
Van der Waal
Forces
Keeps the
Molecules
Together
TYPE OF BONDING
Covalent Network Solids →
Group of solids that contain only covalent bonds and
are made of extremely large molecules.
• Strong covalent bonds therefore very strong substances
• High melting points
• Examples are Diamond or Silicon Carbide
Covalent Crystals: This is a crystal which has
covalent bonding between all of the atoms in the crystal.
 An example of this is a diamond.
Type of bonding
metallic
ionic
covalent
Type of elements
used
Between metals
Metals and nonmetals
Between
nonmetals
Givers &/or takers
of electrons
Between givers
Between givers and
takers
Between takers
Valence e- roam
freely between
many atoms
(delocalized). Sea
of e- surrounding
(+) kernels.
Transfer e-
Share e-
Makes (+) and
(-) ions that are
attracted to each
other.
Forms discrete
molecules.
Description
intermolecular
Van der Waal
forces
Between molecules
Hold covalently
bonded molecules
together as a solid.
Type of material
formed
Solid metallic
elements and alloys
Ceramics and glass
Polymers and
some
ceramics/glasses
Helps form solid
polymers
Strength of bond
Relatively strong
Very strong
Very strong
Weak
Good conductors,
workable, corrode
easily, generally
high melt temps
but variable
Brittle,
high melt temps,
nonconductors as
solids,
don’t corrode
Insulators,
don’t corrode
Help determine a
lot of properties of
covalent compounds
(polymers). Soft
and plastic
Properties
Produced
Formation of Solids Lab