Lecture Notes on Atomic Structure and Bonding

Flashcards reviewing atomic structure and bonding from a materials science lecture.

What are atoms?

Materials are composed of these, which consist of a nucleus (protons and neutrons) and orbitals (electrons).

What is the mass of a proton or neutron?

Approximately 1.66 × 10^-24 grams.

What is Avogadro's number?

0.6023 × 10^23 amu per gram.

What bond is formed when electrons are transferred from one atom to another?

An ionic bond.

What is a key characteristic of ionic bonds regarding their orientation in space?

They are nondirectional.

What force is expressed by: Fc = K(Z1q)(Z2q) / a^2 ?

The Coulombic force of attraction (Fc) between oppositely charged ions, where a is separation distance, K is a constant, Z is ion valence, q is the charge of a single electron, and k is a proportionality constant.

What are the two main sources of the repulsive force (Fr) in ionic bonds?

Overlapping of similarly charged electric fields from each ion, and bringing positively charged nuclei closer.

What is the coordination number (CN)?

The number of adjacent ions surrounding a reference ion or atom.

What is electronegativity?

The ability of an atom to attract electrons to itself.

What is a covalent bond?

Cooperative sharing of valence electrons between two adjacent atoms.

What is the typical bond angle in covalent solids with carbon?

109.5°.

What is a metallic bond?

Electron sharing, but the electrons are delocalized and not bound to any specific atom.

What is secondary bonding (or van der Waals bonding)?

Atomic bonding without electron transfer or sharing.

What are crystalline materials?

Solids in which atoms are arranged in a repeating, three-dimensional pattern.

What is a unit cell?

The smallest structural unit that, when repeated in space, builds the entire crystal lattice.

Into what are crystalline materials organized?

Seven crystal systems and fourteen Bravais lattices.

What is a perfect crystal?

A crystal with no defects, where every atom is in its expected position.

What is the Atomic Packing Factor (APF)?

The fraction of a unit cell’s volume occupied by atoms.

Name common crystal structures (metals):

Body-Centered Cubic (BCC), Face-Centered Cubic (FCC), and Hexagonal Close-Packed (HCP).

Give examples of important ceramic structures:

Cesium chloride (CsCl), sodium chloride (NaCl), fluorite (CaF₂), silica (SiO₂), and corundum (Al₂O₃).

What is the Ionic Packing Factor (IPF)?

The fraction of the unit cell volume occupied by cations and anions.

What are polymers?

Materials made of long, chain-like molecules.

What are the three main parts of the notation system used to describe geometry inside a unit cell?

Positions, directions, and planes.

What does a lattice position tell us?

It tells us where a point is located within the unit cell.

What do lattice directions describe?

Straight lines between two points in the crystal.

What is a family of directions?

A set of geometrically identical directions that are oriented differently.

What does linear density tell you?

How tightly atoms are packed along a certain direction.

What do Miller indices describe?

Planes inside the crystal.

What indices are used for Hexagonal Crystals?

(hkil).

What is a family of planes?

A family of planes contains all planes that are geometrically equivalent due to symmetry.

What are the types of imperfections in Crystalline Structures?

Chemical impurities and structural defects.

Most engineering materials are actually mixtures of different elements

What we call solid solutions.

Why is it Call is called a substitutional solid solution

because one atom substitutes for another

What are known as the Hume-Rothery rules:

for two metals to form a complete substitutional solid solution

What happens in an interstitial solid solution?

the smaller atoms slip into the spaces between them

Solid Solutions in Compounds. Substitution

where nickel oxide (NiO) atoms replace magnesium oxide (MgO) atoms in the crystal

What are known as nonstoichiometric compounds

the number of atoms doesn’t match the ideal chemical formula

What are Point defects

atomic-scale imperfections in a crystal structure that play a key role in diffusion processes

What is Schottky defect

a paired vacancy of oppositely charged ions, necessary to maintain local charge neutrality

What is Frenkel defect

a combination of a vacancy and an interstitialcy, where typically a cation moves from its normal site to an interstitial site

What are Linear Defects. or Dislocations?

one-dimensional imperfections primarily associated with mechanical deformation

What is edge dislocation

an extra half-plane of atoms is inserted into the crystal

What is the Burgers vector (b)

a vector that quantifies the magnitude and direction of the lattice distortion

What is a screw dislocation

involves a spiral distortion of atomic planes around the dislocation line, with the Burgers vector parallel to the line

What are Planar Defects

two-dimensional imperfections that disrupt the regular atomic arrangement over a surface or boundary within the material

What is twin boundary

two regions of a crystal are mirror images of each other

What is a grain boundary

which forms where two single crystals (grains) of different orientations meet

What are Noncrystalline Solids

crystalline materials, noncrystalline or amorphous solids lack long-range atomic order.

A phase is a region within a material that is chemically and structurally uniform is in this governing phase

The Gibbs phase rule

What is The degree of progress or P(t),

is a measure of how far the reaction has proceeded. It is defined as the ratio of functional groups reacted at time t to the initial number of functional groups (at t₀)

the average functionality must be greater than 2

What value has the The average functionality to form at least a linear polymer?

Only dimers can form. The reaction stops after one step

What value has the functionality = 1 in functionaly Concept and Polymer Structure?

is a molecular weight increases gradually in polymers?

Step-Growth Polymerization

What isKinetics of Polymerization

To understand how polymers grow, it’s useful to examine the reaction kinetics—that is, how the concentration of functional groups changes over time

What do define the average number of monomers per polymer molecule

that 𝑋(t) can be non-integer, as it is a statistical average

So, as polymerization

as polymerization progresses (i.e., as P(t) increases), the average molecular weight increases

Which equation defines that this expression shows how a small deviation from stoichiometry dramatically reduces the achievable molecular weight.

The Carothers equation

is defined as: Mm =:NiMi Zi Ni Mi

Number-average molecular weight

on what depends the The shape of the molecular distribution

to the type of polymerization and how far it progresses

What happens in The Mw places even more emphasis on heavier molecules

weight-average molecular weight

A PDI close to 1 indicates a narrow distribution

the distribution of molecular weights

the denominator approaches zero in Gelation concept

for systems with average functionality f > 2

a polymer forms rapidly through the successive addition of monomers to an active site on a growing polymer chain in ?

Chain-Growth Polymerization

Chain-growth mechanisms are classified depends on the charge of the active center in ?

Radical polymerization , Ionic polymerization?

the concentration of all components is uniform throughout the system this happen in:

Homogeneous Polymerization

this Includes only liquid monomers and an initiator, without any solvent process

Bulk Polymerization

homogenous polymerization similar to this one oil-soluble that has viscosity management

Solution Polymerization

type of Heterogeneous polymerization or system

Emulsion the final product contains emulsifying agents, which act as impurities

Why this is more suitable for microemultions or Polydispersity is the width of the bell

the most stable thermodynamically

each solid has a critical surface tension  U = - Ap 2 U

what are Zisman’s rule to spread a solid liquid

where the Si–O backbone and methyl side groups confer PDMS its non-polar, hydrophobic character ?

where these parts are Van der Waals interactions

the polymeric application to tune the spraying parameters with many morphologies surfaces

what is Electrospraying?

what is Sessile or Pendant Drop Method in measure the tension liquid

The contour of a sessile or pendant drop

what is Wilhelmy plate

thin plate is vertically immersed in the liquid Wilermy

of one main contributors to hysteresis

surface roughness

what is plasmaSurface Treatment is most effective for

to increase the Surface purity and wettability of plasma

what it must possess a pH-Responsive

To Enhanced the osteogenesis, and has Antibacterial Cytocompatibility properties

are parts Medical biology that has Surface active Tension related

The tear film, Alveoli and Pulmonary Surfactants

at The CMC properties

That the solution may become opaque in micelles SDS

If the Packing Surfactant Parameter volume is Nₛ = 1/3

spherical micelles

have The droplet size: 0.5–10 µm (visible light wavelength range where more separation are found in

macroemulsions

To Quantify macroermultions how it done

Effective Viscosity , Effective electrical conductivity

To Assess macro emulsions by DLS ?

Dynamic Light Scattering where more aggregation appears the emulsion destabilize ??

Microemulsions use in Vds = nEtR to estimate sizes volume

Volume Calculations

what is Ca = 7 d drop and d drop x 1/Qa/Q, what has the range value??

Capillary number

in realApplications how can the Droplet Generaiont in microfluidic happens the geometries

The flow conditions, Flow-Focusing and co-Flow