Material Science

Atomic Mass

Atomic Mass

The mass of an individual atom

Atomic Weight

Average of the atomic masses of an atom’s isotope

amu

average of proton rest mass and the neutron rest mass used for expressing masses of atoms, molecules or nuclear particles.

Force of attraction

FA =( 1/ 4πε0 * r2) (q1e)(q2e)

At the equilibrium separation-distance the sum of attractive and repulsive forces

zero

net potential energy between 2 adjacent ions

EN = ( - A / r ) + ( B / r^n)

curve of EN versus r is a ………. at E0

minimum

E0 is

bonding energy

Ionic bonding

electrostatic attraction between oppositely charged ions.

Covalent bonding

electron sharing between two adjacent atoms such that each atom assumes a stable electron configuration.

metallic bonding

positively charged ion cores are shielded from one another, and also "glued" together by the sea of valence electrons.

Pauli exclusion principle

each electron state can hold no more than two electrons, which must have opposite spins. \n

equilibrium spacing between two atoms occurs when

bond energy (FN) is minimum , so FN = 0

As the atomic \n bonds are stretched the atoms

attract each other

when the atomic bonds are compressed the atoms

repel each other

sp3 hybridization

the mixing character of one 2s-orbital and three 2p-orbitals to create four sp3 \n hybrid orbitals with similar characteristics.

draw a px orbital

draw a py orbital

draw a pz orbital

P orbitals have a ……. shape

dumbell

Van der Waals bonding

relatively weak attractive force between atoms or nonpolar molecules caused by a temporary change in dipole moment arising from a brief shift of orbital electrons to one side of one atom or molecule, creating a similar shift in adjacent atoms or molecules.

Hydrogen bond

primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to N / O / F

% Ionic character =

1 - e^[-(0.25)(electronegative value for more electronegative element - Xb) ] x 100

If %IC = 0 and the elements are metal it is ……. bonding

metallic

atomic structure

relates to the number of protons and neutrons in the nucleus of an atom and the number and \n probability of distributed electrons.

crystal structure

pertains to the arrangement of atoms in a crystalline s

FCC a =

2Rroot2

BCC a =

4R / root3

V =

a ^3

FCC amount of atoms in unit cell is

4

Number of atoms per unit cell

Ni + (Nf / 2 ) + (Nc / 8)

# of atoms for FCC

4

FCC coordination number

12

APF =

volume of atoms in a unit cell / unit cell volume

number of atoms in BCC cell

2

Vc for FCC

16R^3*root2

Vs for BCC

(4/3)piR^3*

FCC APF

0.74

Vs for FCC

(16/3)pi*R^3

Vc for BCC

64*R^3 / 3root3

BCC APF

0.68

HCP number of atoms

6

Vc for HCP

6R^2height**root3

HCP Area

3a^2*root3 / 2

HCP APF

0.74

Vs for HCP

8piR^3

theoretical density for metals =

nA / VcNa

polymorphism

The ability of a solid material to exist in more than one form or crystal structure.

Allotropy

The possibility of the existence of two or more different crystal structures for a substance

angle of diffracted beam equation

nλ = 2d(hkl)sin θ

Linear Density

number of atoms centered on direction vector / length of direction vector

Plane Density

number of atoms centered on plane / area of plane

area of (100) plane

root2 * a^2

Number average molecular weight

Mn

Mn =

Sum Xi *Mi

Dp =

Mn / m (repeat unit weight)

DP is

number of repeat units along an average chain

Thermoset

material that strengthens when heated but cannot be remolded or heated after the initial forming

thermoplastics

can be reheated, remolded and cooled as necessary without causing any chemical changes. \n

thermoplastic is synthesized by

addition polymerization

thermosets are synthesized by

condensation polymerization

thermoplastics have ….. between molecular chains

secondary

Have ……. bonds between molecular chains and are \n held together by strong ……..

primar bonds / cross-links

thermoplastics have …… molecular weight compared to thermosets

number of vacancies =

Ne^(-Qv/kT)

Fraction of lattice sites =

Nv / N

Ns =

Ne^(-deltaH / R (1/T2 - 1/T1)

for BBB h + k + l is

even

for FCC h , k , l are

either all odd or all even