Solid State Flashcards
(26 cards)
Isomorphic Substances
two or more substances having the same chemical structures. they have the same chemical composition but different atomic ratios
Polymorphous Substances
a single substance that occurs in 2 or more forms as a crystal due to differnt conditions
Allotropy
polymorphism existing in elements
How are crystals classified
ionic, covalent, molecular, metallic
How do ionic crystals form
when charged ions are held together by electrostatic force due to oppositely charged ions as cations and anions differ in size.
State the properties of an ionic crystal
hard and brittle, have high melting points, bad conductors of electricity in its solid state but good conductors when dissolved in water
like: NaCl, KCl
How do covalent network crystals form
when atoms are linked together by covalent bonds resulting in strong & rigid structure as the bonds form a network. the electrons are localized and immobilized
State the properties of a covalent network crystal
hard and incompressible, high melting and boiling points, poor conductors of heat and electricity
like: quartz and diamond
How do molecular crystals form
when molecules are held together by weak intermolecular forces like weak dipole - dipole interactions, London forces, intermolecular hydrogen bonds.
What are molecular crystals
when cl2, ch4, h2, co2 & o2 solidifies and crystalline organic compounds
State the properties of a molecular crystals
they are soft, low melting points, poor electric conductors, good insulators
How do metallic crystals form
when atoms of the same element held together by a metallic bond
State the properties of a metallic crystal
they are malleable, they are ductile, good conductors of heat & electricity
like: Na, K, Fe
What is a metallic bond
in a solid state the valence electrons are delocalized over the entire crystal leaving behind a positively charged metal ion (an array of the positive ions immersed in a sea of a mobile electron). these attractive interactions between cations and mobile electrons constitute metal bonds
Define lattice
a geometrical arrangement of points in a dimensional periodic array
How is a crystal lattice obtained
when a constituent particle to each lattice point forming a basis of crystal lattice
Define a crystal
a structure that results by attracting a basis to each lattice point
Define unit cell
the smallest repeating structural unit of crystalline solid
how is a crystal generated
the space lattice of a crystal is built up of a 3d basic pattern. which is repeated in all dimensions to generate an entire crystal. Unit cells are stacked together to form a crystal. Each unit cell shares faces, edges, and corners with its neighbors.
Types of unit cell
- Primitive unit cell
- Body centered unit cell
- Face centered unit cell
- Base centered unit cell
Where are the constituent particles present:
1. Primitive unit cell
2. Body centered unit cell
3. Face centered unit cell
4. Base centered unit cell
- only at the corners
- center of a body and corner particles
- center of each face and corner particles
- at the center of faces and corner particles
Bravais lattices
when these lattices crystal structures of 14 different space lattices in which similar points that can be arranged in a 3d
the 7 crystal systems of bravais lattices
- cubic system
- Tetragonal system
- Orthorhombic system
- Rhombohedral system
- Monoclinic system
- Triclinic system
- Hexagonal system
Why do crystal defects occur
They occur during the process of crystallization. when the crystallization occurs at a faster rate. Sometimes they are intentional to create desired properties of a crystal
