Chapter 2 Flashcards
The elements listed in the Periodic table can be divided into three categories. Examples
metals (iron), non metals (carbon), semimetals (silicon)
Which elemets are the noble metals, and why are they named noble
Copper, silver, and gold (medals). REsistant to corrosion
Describe ionic bonding
Atoms of one element give up the electron to another atom of another element
What is the difference between noncrystaline and crystaline structures
The atoms in a crystalline structure are located in a regular and repeating lattice position in three dimensions. These possess a long range order which allows high-packing density. The atoms in an amorphous structure do not follow any pattern
What is the difference between primary and secondary bonding in the structure of materials
Primary is a strong bonding (Ex: molecule), Secondary bonding is not strong (Ex: general attraction between molecules in material)
What are some common point defects?
VAcancy: missing atom, ion-pair vacandy: missing pair of ions, Interstitalicy: distortion in the lattice caused by an extra atom, Frenkel defect: an ion is removed from he regular position and inserted into a interstitial position
Define the difference between elastic and plastic deformation in terms of the effect on the crystal lattice structure
Elastic deformation involves a temporary distortion of the lattice structure that is
proportional to the applied stress. Plastic deformation involves a stress of sufficient magnitude to
cause a permanent shift in the relative positions of adjacent atoms in the lattice. Plastic deformation
generally involves the mechanism of slip - relative movement of atoms on opposite sides of a plane in
the lattice
How do grain boundaries contribute to the strain-hardening phenomenon in metals?
Grain boundaries block the continued movement of dislocations in the metal during
straining. As more dislocations become blocked, the metal becomes more difficult to deform; in
effect it becomes stronger.
Identify some materials that have a crystalline structure
MEtals and ceramics (NOT GLASS), and very few polymers
Identify some materials that posses a noncrystaline structure
glass and certain plastics
what is the basic difference in the solidification process between crystalline and noncrystalline structures
Crystalline structures undergo an abrupt volumetric change as they transform from liquid to solid state and vice versa. This is accompanied by energy called the heat of fusion that must be added to the material during melting or released during solidification. Noncrystalline material without these things.
The basic structural unit of matter is which of the following (a) atom, (b) electron, (c) element,
(d) molecule, or (e) nucleus?
a atom
Approximately how many different elements have been identified (one best answer): (a) 10, (b) 50,
(c) 100, (d) 200, or (e) 500?
c 100
In the Periodic Table, the elements can be divided into which of the following categories (a) ceramics, (b) gases, (c) liquids, (d) metals, (e) nonmetals, (f) polymers, (g) semi-metals,
and (h) solids?
d metals, e nonmetals, g semimetals
The element with the lowes density and smallest atomic weight is which of the following: (a)
aluminum, (b) argon, (c) helium, (d) hydrogen, or (e) magnesium?
d hydrogen
Which of the following bond types are classified as primary bonds (three correct answers): (a)
covalent bonding, (b) hydrogen bonding, (c) ionic bonding, (d) metallic bonding, and (e) van der
Waals forces?
a covalent, c ionic bonding, d metallic bonding
How many atoms are there in the FCC (face-centered cubic), BCC (Body-centered cubic), and, HCP (hexagonal close-packed) unit cell (a) 8, (b)
9, (c) 10, (d) 12, or (e) 14 (f) 17
FCC: e 14, BCC: b 8. HCP F 17
Which of the following are not point defects: (three correct answers): (a)
edge dislocation, (b) grain boundaries, (c) interstitialcy, (d) Schottky defect (ion-pair), (e) screw dislocation, or
(f) vacancy?
c interstitalcy, d Schottky defect, f vacancy
Which one of the following crystal structures has the fewest slip directions (therefore more difficult to deform at room temp) (a) BCC, (b) FCC, or (c) HCP?
c HCP
Grain boundaries are an example of which of the following types of crystal structure defects (a) dislocation, (b) Frenkel defect, (c) line defects, (d) point defects, or (e) surface defects?
(e) surface defects
Twinning is in which of the following (three best answers): (a) elastic deformation, (b) mechanism of
plastic deformation, (c) more likely at high deformation rates, (d) more likely in metals with HCP
structure, (e) slip mechanism, and (f) type of dislocation?
b mechanism of plastic deformation, c more likely at high deformation rates, d more likely with metals with HCP structure
Polymers are characterized by which of the following bonding types (two correct answers): (a)
adhesive, (b) covalent, (c) hydrogen, (d) ionic, (e) metallic, and (f) van der Waals?
b covalent, f van der Waals
What are the secondary bonds
Dipole forces, London forces, (van der waals for previous two) Hydrogen bonding
covalent bonding?
Electrons are shared between atoms
Metalic bonding?
electrons shared as electron cloud
Dipole forces
Come form molecules that have two atoms that have opposite electric charges. The positive side of the atom attracts the negative side
London forces
Force between non-polar molecules, because elctrons are moving rapidly, a gap forms in the atom, and that exposes the proton, making a small positive charge
Hydrogen bonding?
Hydrogen atoms are aligned to one side of the atom (or molecule) creating a positive charge (like in water), that atracts the negative charge of other molecules with similar polarity (like water again)
Draw BCC structure
has atom at center
Draw FCC
has atom on each face
Draww HCP
Hexagon, three in middle
Types of defects in crystals
point, line, and surface
types of point defects
vacancy, interstitalcy, frenkel defect
vacancy?
missing atom or ion
intersttialcy
extra atom
Frenkel
displaced ion. Ion in a place it’s not supposed to be
Why do defects happen?
usually while solidifying, grain boundries end up colliding with each other and can’t form propper ones
Edge dislocation
Extra palne of atoms
types of Line defencts
edge dislocation, screw dislocation
screw dislocation?
Spiral within the lattice structure. It looks like an imperfection line
Surface defects?
Defects extend in two directions (like shear stress
What happens to atoms in elastic strain
they just stretch a bit
What happens to atoms in plastic strain
They snap, or rather shift
Explain twinning
Another method of plastic deformation,
Main differences between crystalline and non crystalline materials
No order of molecules, differen melting and thermal expansion characteristics
