study guide Flashcards
an atom is composed of ______; __________ and ___ except ___________(which element), the nucleus of which does not have neutron
proton; neutron, electron, hydrogen
atomic number is equal to the number of ______ in a nucleus of an atom; and the number of _________ of a neutral species
protons
electrons
the electrons that occupy the outermost filled shell are also called __________ electrons
valence
the predominant type of bonding for titanium is __________
metallic
electrons tend to occupy the ______ available energy states
lowest
what does electronegativity represent? metallic elements or non metallic elements?
?non metallic
to form ionic bonding ______ electronegativity difference between two elements are required; what about to form covalent bonds?
large are required????
small ones are required for covalent bonds
what is the primary bonding of NaCl? what about CO2? what about Fe?
ionic —> covalent —–> metallic
secondary bonding arises from the interactions among __________, typically, __________ have significant amount of secondary bonding
dipoles.
polymer
which has higher bonding energy?
primary bonding
high bonding energy usually leads to ______ thermal expansion and _________ melting temperature
low thermal expansion
high melting temperature
crystalline structures and amorphous structures, which usually has more dense packing atoms? which have orderly structures?
crystal - have high density
crystal will have orderly structures
most engineering materials are ________
polycrystals
properties of ____ may/or may not vary with direction; while properties of _____________ vary with directoin
polycrystals- may or may not vary with direction
single crystal vary with direction
two steps of solidification process are ________ and __________
nuclei form and nucleic growth
atoms at grain boundary area have high reactivity and mobility
true
the equilibrium concentration of point defects increases with temperature (t/F)
true
know structures of three different types of point defects
substitutional, interstitial, vacancies
in substistitutional solid solution, the impurity atoms occupy the atomic sites in crystal lattice (t/F)
T
Ni in Cu is interstitial solid solution (t/f)
false its substitutional. because atom radi are to close in size
in __________ dislocation, the burgers vector is parallel to the dislocation line; in _________ dislocation, the dislocation motion shows spiral pathway; in _______ dislocation, there is an extral half-plane of atoms. to describe the lattice distortion caused by dislocations; the parameter _________ is used
line dislocation
skew dislocation
edge dislocation
burgers vector
diffusion phenomenon could only occur between different materials (t/f)
false. interdiffusion
to form substitutional solid solution, _______________ sites in crystal are needed becasue of __________ mechanism
vacancies sites
because of vacancy mechanism
two diffusion mechanisms introduced in the class are _______ and _________
vacancy and intersitial
vacancy diffusion and interstitial diffusion, which one needs a higher activation energy?
vacancy diffusion
vacancy diffusion rate depends on ____________ and ____________
activation energy, and number of vacancies
