Exam 1 Flashcards
Write the electron configuration for Fe3+ (the atomic # for Fe is 26)
Fe3+ has 23 e-
1s2 2s2 2p6 3s2 3p6 3d3 4s2 (would accept 3d5)
Define electronegativity
a measure of how strongly atoms attract bonding electrons to themselves
measures how tightly e- are bound to an atom
What is the nearest neighbor direction in FCC crystals? BCC crystals?
FCC: <110>
BCC: <111>
What are the 3 types of primary bonds discussed in this class?
Metallic
Ionic
Covalent
What are 2 examples of 0-dimensional (point) defects in crystals?
Vacancies
Frankel
Schottky
Substitutional
What are the 2 types of 1-dimensional (linear) defects in crystals?
Edge
Screw
(With perpendicular symbol before each)
What is one type of 2-dimensional (planar) defects in crystals?
Grain boundary
What is a Schottky defect?
Both cation and anion missing from an ionic structure. 2 vacancies
What is a Frankel defect?
2 cations occupy one lattice site. 1 vaccancy
What is a dipole?
A pair of equal and oppositely charged or magnetized poles separated by a distance. Associated with secondary bonding
Why are H bonds so much stronger than Van der Waals forces?
H only has one e-. when it gets pulled to one side, it leaves onyl the + nucleus exposed
What is the coordintation number for the BCC crystal structure? For the FCC structure?
BCC: 8
FCC: 12
What are hybrid orbitals? Give one example
sp orbitals combine to form a new bond geometry
sp2: sp3 orbitals in graphite, diamond
Define covalent bonding, when does it occur?
Adjacent atoms share electrons: occurs when electronegativities are equal to each other
Define metallic bonding
Lattice of + ion cores surrounded by a sea of e-
What is a side group?
Atom or molecule attached to the carbon backbone of a polymer chain.
What is the difference between thermosets and thermoplastics?
Thermoplastics can be heated: reformed. Thermo sets will char before flowing.
Write the electron configuration for calcium (Ca, atomic # = 20)
1s2 2s2 2p6 3s2 3p6 3d2
Define a thermoset polymer
- A polymer that will burn/char before reforming/melting when heated.
- A polymer with primary bonds along the chains and between adjacent chains
Van der Waals bonds involve what type of atoms or molecules?
dipoles