GeotechnicalEngineeringResearchLaboratory
OneUniversityAvenue
Lowell,Massachusetts01854
Tel:(978)934‐2621
e‐mail: [email protected]
website:http://faculty.uml.edu/ehajduk
EdwardL.Hajduk,D.Eng,PE
Lecturer
PA105D
Fax:(978)934‐3052
DEPARTMENTOFCIVILANDENVIRONMENTALENGINEERING
14.310 ENGINEERING MATERIALS
Exam #1: Atoms, Unit Cells, Directional and Millar Indices, and X-ray
Diffraction
Questions (2 Points Each - 20 Points Total):
1. In your own words, describe the structure of an atom. List all the major parts.
Electrons (surrounding the nucleus).
neutrons (if present)
Nucleus consisting of protons and
2. Most elemental metals (about 90%) crystalize upon solidification into three common
densely packed crystal structures. Name these three structures along with their
common abbreviations.
BCC – Body Centered Cubic; FCC – Face Centered Cubic; HCP – Hexagonal
Close Packed
3. Write the equation that allows someone to determine the interplanar distance
between two closest planes with the same Miler indices and detail the variables of
this equation.
a
Where: a = lattice constant, d = distance between planes,
d hkl h 2 k 2 l 2
and hkl = Miller Indices
4. In your own words, describe a metallic bond.
The type of chemical bond between atoms in a metallic element, formed by the
valence electrons moving freely through the metal lattice.
5. In your own words, define principal quantum number.
The principal quantum number (n) describes the size of the orbital (main energy
levels).
6. Write the equation for Braggs Law (using an order of diffraction of 1) and detail the
variables.
2dSin
Where: λ = X-ray wavelength, d = distance between planes, and
θ = scattering angle.
For Questions #7 and #10, use the following periodic table of elements:
Row 1
Column 1
7. What is the atomic number for Zinc (Zn)?
30
8. What is the atomic mass of Potassium (K)?
39.10 amu (atomic mass units)
9. For Column 1 (highlighted by the solid line in the provided periodic table), does
atomic radius increase or decrease when going from Hydrogen (H) to Francium
(Fr)? Briefly explain why.
Increase. The valence electrons reside in orbitals of increasing size going from H
to Fr. Therefore, the atomic radii increase.
10. For Row 1 (highlighted by the dashed line in the provided periodic table), does
atomic radius increase or decrease when going from Sodium (Na) to Argon (Ar)?
Briefly explain why.
Decrease. As more protons are added to the nucleus from Na to Ar, this
increases the effective nuclear charge, which “pulls” the electrons closer to the
nucleus, decreasing the atomic radii.
14.310 2015 Exam 1 Solution
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EXTRA CREDIT: (5 points)
What are the direction indices for a line perpendicular to the 110 plane?
110
USEFUL INFORMATION?
14.310 2015 Exam 1 Solution
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