Solids, Properties, Alloys

What are the four types of atom arrangements in solids

• Ionic solids

• Molecular solids

• Network Covalent solids

• Metallic solids

What are formula units

Repeating units in three dimensions with no distinct molecules

Arrangement of Ionic Solids

• attractive forces

• types of atoms

• arrangement of atoms

• bonds/forces broken upon melting

• individual particles in liquid after melting

• ionic bonds

• atoms are metals and nonmetals

• formula units

• ionic bonds broken

• ions

Arrangement of Molecular Solids

• attractive forces

• types of atoms

• arrangement of atoms

• bonds/forces broken upon melting

• individual particles in liquid after melting

• Intermolecular forces

• all atoms are nonmetals

• molecular structure

• IMFS broken

• molecules

Arrangement of Network Covalent Solids

• attractive forces

• types of atoms

• arrangement of atoms

• bonds/forces broken upon melting

• individual particles in liquid after melting

• Covalent bonds

• all atoms are nonmetals

• formula units

• covalent bonds broken

• atoms

Arrangement of Metallic Solids

• attractive forces

• types of atoms

• arrangement of molecules

• bonds/forces broken upon melting

• individual particles in liquid after melting

• Metallic bonds

• all atoms are metals

• formula units

• ionic bonds broken

• metal ions

Which type of solid has the lowest melting points?

Molecular

Which type of solid has the lowest enthalpies of fusion?

Molecular

Which type of attractive forces is the weakest?

Rank them in order from strongest to weakest.

• IMF is the weakest

• covalent > metallic ≥ ionic > IMF

For a substance to be soluble in water it must be

charged or polar

For a substance to be conductive it must be

charged particles in a mobile state

Solubility/conductivity of Ionic Solids

• Very soluble

• Conductive after they are melted bc ions flow in liquid

• Not conductive as solids bc ions are fixed

Solubility/conductivity of Molecular Solids

• Can be soluble

• generally non-conductive

Solubility/conductivity of Metallic Solids

• least soluble (generally not)

• most conductive even in solid state bc electrons are delocalized and free to flow

Solubility/conductivity of Network Covalent Solids

• Least soluble

• Generally non-conductive

2 reasons why conductivity for some substances would not exist

1. substances are not soluble in water

2. water is not an aq solution

What are alloys

Mixed metals that have properties that benefit us

Interstitial vs Substitutional alloys

• Interstitial: element fits in gaps between metal

• Substitutional: element replaces metal

Interstitial Alloys

• component atoms size

• component atoms are different sizes

Substitutional Alloys

• component atoms size

• component atoms are similar sizes

When are solids the most stable?

• Minimized bond length

• Maximized bond strength

• Maximized number of atoms “touching” one another/fill space most efficiently

Why would an interstitial alloy not form a stable crystal structure if the component atoms were similar sizes?

• Bond length would increase → decreases strength

Why would an substitutional alloy not form a stable crystal structure if the component atoms were different sizes?

• bond length would increase → strength decreases

Do substitutional alloys have a density similar to/greater than/less than the pure metal

• Similar bc the particles are similar size and mass

Do interstitial alloys have a density similar to/greater than/less than the pure metal

• slightly greater because spacing between metal atoms might increase

Is interstitial or substitutional more rigid

Interstitial because it has a greater number of attractions

What causes differences between mild steel, medium steel, and high carbon steel

• amount of carbon added into alloy