Crystals-Crystals are solid materials whose atoms are arranged in an orderly,
repeating pattern extending in all three spatial dimensions
Crystal Structure- The crystal structure refers to the specific way in which atoms,
ions, or molecules are arranged in a crystal. This structure is characterized by a repeating
unit called a “unit cell,” which serves as the building block for the entire crystal lattice.
BCC)body-centered cubic
(FCC)face-centered cubic
Lattice Structure: he arrangement of atoms in a crystal can be visualized as a grid,
or “lattice,” where each point in the lattice represents the position of an atom.
Symmetry: Crystalline structures are highly symmetrical. The symmetry can vary
depending on the material, but all crystals exhibit some form of symmetry, which influences
their physical properties, like strength, electrical conductivity, and optical behavior. Example: The salt crystal (sodium chloride)
Types of Crystal Structures:
1. Body-Centered Cubic (BCC)–atoms
are positioned at each of the eight corners of
a cube, BCC structure are generally strong and hard
2. Face-Centered Cubic (FCC)- This arrangement allows for a higher
packing density, meaning the atoms are more
closely packed together.
Examples of FCC metals include aluminum, copper, and
gold.
3. Hexagonal Close-Packed (HCP) different from the cubic structures in that it
has a hexagonal shape.
Properties Influenced by Crystal Structure
- Strength:
- Flexibility
- Density:
Metals
-
- a class of elements characterized by their unique physical properties
- typically
hard, strong, and capable of withstanding high forces, making them suitable for structural
and load-bearing applications. - They are also highly conductive, both electrically and
thermally, which is essential in electronic and heat management applications. - They are versatile
materials, capable of being alloyed (combined with other elements) to enhance specific
properties like strength, durability, or corrosion resistance.
- Common Properties of Metals
- High Strength:they can
withstand stretching forces - Conductivity: excellent conductors of electricity and heat due to their
unique atomic structure. - Malleability:they can be hammered or rolled into
thin sheets without breaking. - Luster: have a shiny appearance (metallic luster) because they reflect light
effectively
- High Strength:they can
- Types of Metallic Structures
- Metallic Bonding: where free electrons move throughout a “sea of electrons” around positively charged metal
ions. - each metal atom donates one or more of its outer electrons to
form a collective pool of electrons.
- Metallic Bonding: where free electrons move throughout a “sea of electrons” around positively charged metal
- Grain Boundaries: they play a
significant role in determining a metal’s properties. can influence the strength, hardness,
and durability of metals.
Iron, in its
pure form, is relatively soft and prone to rusting. most widely
used engineering materials due to its high strength
and relatively low cost.
Aluminum is a
lightweight metal with excellent corrosion resistance.good thermal and electrical conductivity, though not as high
as copper.
Copper is well-known for its
excellent electrical and thermal conductivity, second only to silver. widely used in electrical wiring,
motor windings, and plumbing due to its high conductivity and
corrosion resistance. copper is used in heat exchangers,
radiators, and air conditioning systems because of its ability to
transfer heat efficiently.
Β
Polymers
-
- large molecules made up of long chains of repeating units called monomers.
- monomers are bonded together in a process called polymerization, forming
complex structures that can be linear, branched, or cross-linked - Polymers are incredibly versatile due to the variety of possible monomers
and structures.
- Types of Polymers
- Thermoplastics– polymers that can be repeatedly melted and reshaped
upon heating. - Thermosets-thermosets have a rigid, cross-linked structure, which
makes them hard and inflexible once they are set. making it impossible
to remelt or reshape. - Elastomers–highly elastic properties, meaning
they can be stretched and return to their original
shape.
- Thermoplastics– polymers that can be repeatedly melted and reshaped
- Nanomaterials-about 100,000 times smaller than the width of
a human hair.
Types of Nanomaterials
-
- Nanoparticles–spherical particles with
diameters in the nanoscale range. - Nanotubes- cylindrical structures with
unique properties, especially when made of
materials like carbon
- Nanoparticles–spherical particles with
- Applications of Nanomaterials
- Electronics: Nanomaterials are used in
the electronics industry to create
smaller, faster, and more efficient
devices. - Medical Treatments: In medicine,
nanomaterials are used in drug
delivery, imaging, and diagnostics. - Coatings: Nanomaterials are used in coatings to improve durability, resistance to
scratches, and even antibacterial properties. - Energy Storage: Nanotechnology is revolutionizing energy storage, especially in batteries
and supercapacitors.
- Electronics: Nanomaterials are used in
-
NUCLEAR CHEMISTRY
- TYPES OF NUCLEAR DECAY
- ALPHA DECAY -HE reaction in which alpha particle is ejected
- BETHA DECAY-neutron decays into a proton and electron
- GAMMA DECAY-high energy poton release
- ELECTRON CAPTURE-the first shell is captured by nucleus
- POSITRON EMISSION