ISU MATE Mod1 2026

Bonding Forces

Forces that attract atoms and repel atoms from each other when trying to form a bond

Potential Energy

potential energy PE between the two atoms for both attraction and repulsion as a function of separation distance r are given by EA and ER

Coulombs Law

The force F between two charged particles as a function the magnitude of the two charges and r, the distance between them.

Attraction Force

The force of attraction FA between two oppositely charged particles as a function of distance r between them

Force & Potential Energy for Repulsion

The repulsive force FR and associated potential energy ER are electrostatic & QM in nature. As a function of distance r between the two ions

Covalent Bonding

The attractive force is between ion cores and the valence electrons that are located or “localized” in the shared orbitals

Directional attraction, dictated by shapes of orbitals

Metallic Bonding

The attractive force is between ion cores and the valence electrons that are “delocalized” in the “sea” of electrons

Non-directional attraction, dictated by attraction to “sea”

Ionic Bonding

Attractive forces are electrostatic

Non-directional attraction, limited by like charge repulsion

Amorphous Materials

Materials that don’t exhibit crystallinity

Single Crystals

Materials made up of one single crystal. All the atoms in the bulk material are perfectly periodic. Single crystals are rare or human-made

Polycrystalline

An assemblage of single crystals also known as grains.

Each with different orientations relative to each other and separated by grain boundaries

Atomic Structure

The “little” picture of structure. Describes How the atoms are arranged in crystals or grains

Lattice

An array of positions or points in space. A geometric framework on which to “hang” or “position” atoms

Unit Cell

The smallest repeat unit which defines a lattice

Lattice Parameters

Unit cell dimensions give by a, b and c

Cubic Bravais Lattices

There are 3 cubic Bravais lattices in the cubic crystal system defined as having all 90 degree angles and equal side lengths

Basis

A simple geometric “recipe” for placing atoms on, or about, a lattice point

Polymorphism

A material that can exist in more than one form or structure

Elastic Lattice Energy

The energy required to separate an ionic crystal into its constituent ions

SC

FCC

BCC

HCP

Induced Dipole Bonds

Weakest, asymmetrical bonds

Thermal fluctuations cause temporary electrical asymmetry in non-polar atoms & molecules. These can induce similar polarizations in adjacent atoms.

Polar Molecule-Induced Dipole Bonds

Charge asymmetry in polar molecules can induce dipoles in non-polar molecules

Permanent Dipole Bonds

Hydrogen bond, strongest bond

Polar-to-polar molecule bonding

Van der Waals Bonds

Several types of secondary bonds exist.

All are weak compared to primary bonding

Each is the result of attraction due to partial charge electric dipoles that exists between all atoms or molecules.