MTL 200 NEED TO KNOW EXAM
QUESTIONS WITH 100% CORRECT
ANSWERS LATEST VERSION 2025/2026.
What is an isotope? - ANS Atoms of the same element that have different numbers of
neutrons
What is the Pauli Exclusion Principle? - ANS each electron state can hold no more than two
electrons which must have opposite signs
What is the Stable Electron Configuration? - ANS the state within the outermost shell
completely filled (ex. inert gases: He, Ne, Ar, etc)
What is bonding energy? - ANS the energy required to separate two atoms that are
chemically bonded to an infinite distance (units: kJ/mol or eV/atom)
Which kinds of bonds are nondirectional? Which are directional? - ANS Nondirectional: ionic
bonding, metallic bonding
Directional: covalent bonding
What is the difference between directional and nondirectional bonding? -
ANS Nondirectional: magnitude of the bond is equal in all directions around an ion
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,Directional: atoms need to be in a specific orientation
What is the relationship between the unit cell edge length and the atomic radius for FCC crystal
structures? - ANS a = unit cell edge length
R = atomic radius
a = 2Rsqrt(2)
How many atoms are in the FCC structure? - ANS 4 atoms
What is the relationship between the unit cell edge length and the atomic radius for BCC crystal
structures? - ANS a = (4R)/sqrt(3)
How many atoms are in the BCC structure? - ANS 2 atoms
What is the relationship between the unit cell edge length and the atomic radius for HCP crystal
structures? - ANS a = 2R
How many atoms are in the HCP structure? - ANS 6 atoms
What is the formula for volume of HCP unit cell in terms of a and c? - ANS V=
(3ca^2sqrt(3))/2
What are the coordination numbers of FCC, BCC, and HCP structures? - ANS FCC: 12
BCC: 8
HCP: 12
What are the APF of FCC, BCC, and HCP structures? - ANS FCC: 0.74 or 74%
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, BCC: 0.68 or 68%
HCP: 0.74 or 74%
What is the formula for the volume of 4 atoms in FCC? - ANS V=4*(4/3)(piR^3)
What is polymorphism? What is it called for elements? - ANS - the phenomenon of a solid
material existing in more than one form of crystal structure.
- for elements, it is called allotropy
What coordinate form do you use for crystallographic directions for cubic structures, hexagonal
structures and for a family of equivalent directions? - ANS Cubic structures: [UVW]
Hexagonal structures: [uvtw]
Family of equivalent directions: <uvw> <uvtw>
How do you convert [UVW] to [uvtw]? - ANS u = (1/3)(2U-V)
v = (1/3)(2V-U)
t = -(u+v)
w=W
What is the formula for linear density (LD)? - ANS LD = (# of atoms centered on a direction
vector)/(length of direction vector)
What kind of brackets are used for linear? ( ) or [ ]? - ANS []
What is the formula for planar density? (PD) - ANS PD = (# of atoms centered on a
plane)/(area of a plane)
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS WITH 100% CORRECT
ANSWERS LATEST VERSION 2025/2026.
What is an isotope? - ANS Atoms of the same element that have different numbers of
neutrons
What is the Pauli Exclusion Principle? - ANS each electron state can hold no more than two
electrons which must have opposite signs
What is the Stable Electron Configuration? - ANS the state within the outermost shell
completely filled (ex. inert gases: He, Ne, Ar, etc)
What is bonding energy? - ANS the energy required to separate two atoms that are
chemically bonded to an infinite distance (units: kJ/mol or eV/atom)
Which kinds of bonds are nondirectional? Which are directional? - ANS Nondirectional: ionic
bonding, metallic bonding
Directional: covalent bonding
What is the difference between directional and nondirectional bonding? -
ANS Nondirectional: magnitude of the bond is equal in all directions around an ion
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,Directional: atoms need to be in a specific orientation
What is the relationship between the unit cell edge length and the atomic radius for FCC crystal
structures? - ANS a = unit cell edge length
R = atomic radius
a = 2Rsqrt(2)
How many atoms are in the FCC structure? - ANS 4 atoms
What is the relationship between the unit cell edge length and the atomic radius for BCC crystal
structures? - ANS a = (4R)/sqrt(3)
How many atoms are in the BCC structure? - ANS 2 atoms
What is the relationship between the unit cell edge length and the atomic radius for HCP crystal
structures? - ANS a = 2R
How many atoms are in the HCP structure? - ANS 6 atoms
What is the formula for volume of HCP unit cell in terms of a and c? - ANS V=
(3ca^2sqrt(3))/2
What are the coordination numbers of FCC, BCC, and HCP structures? - ANS FCC: 12
BCC: 8
HCP: 12
What are the APF of FCC, BCC, and HCP structures? - ANS FCC: 0.74 or 74%
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, BCC: 0.68 or 68%
HCP: 0.74 or 74%
What is the formula for the volume of 4 atoms in FCC? - ANS V=4*(4/3)(piR^3)
What is polymorphism? What is it called for elements? - ANS - the phenomenon of a solid
material existing in more than one form of crystal structure.
- for elements, it is called allotropy
What coordinate form do you use for crystallographic directions for cubic structures, hexagonal
structures and for a family of equivalent directions? - ANS Cubic structures: [UVW]
Hexagonal structures: [uvtw]
Family of equivalent directions: <uvw> <uvtw>
How do you convert [UVW] to [uvtw]? - ANS u = (1/3)(2U-V)
v = (1/3)(2V-U)
t = -(u+v)
w=W
What is the formula for linear density (LD)? - ANS LD = (# of atoms centered on a direction
vector)/(length of direction vector)
What kind of brackets are used for linear? ( ) or [ ]? - ANS []
What is the formula for planar density? (PD) - ANS PD = (# of atoms centered on a
plane)/(area of a plane)
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
