Several elements exist as diatomic molecules

• Iodine is a solid of weakly-bonded diatomic molecules

• H2, N2, O2, F2, Cl2, Br2, I2

Elements stack atoms to form solids in different ways.

Stacking Patterns:

Solid elements display various forms called allotropes.

Carbon: diamond graphite buckminster fullerene

Phosphorus:

https://www.webelements.com/compounds/iron/iron_sulphide.html

Sodium chloride consists of sodium cations and chloride anions stacked in a cubic arrangement.

Calcium cations and phophate anions are bonded through ionic forces in calcium phosphate.

https://en.wikipedia.org/wiki/Dicalcium_phosphate

https://nutricorn-co.en.made-in-china.com/product/fMjnrdmCrZUF/China-High-Quality-Dicalcium-Phosphate-DCP-Mineral-Chemical-Products.html

Lots of elements form oxides.

Some oxides behave like acids, some like bases, and some can do both.

https://www.webelements.com/compounds/iron/iron_sulphide.html

Iron (II) sulfide is a mineral called pyrite, which resembles gold.

https://www.amazon.com/Natural-Pyrite-Cube-Matrix-Beautiful/dp/B01MEF8PPC

Silicon and oxygen bond covalently in multiple ways to create a variety of network solids.

• obsidian

• quartz

Sucrose (table sugar) is a molecular solid.

https://crystallography365.wordpress.com/2014/01/12/sweet-crystallography-the-crystal-structure-of-sucrose/

https://en.wikipedia.org/wiki/Sucrose

• Molecules of sucrose are stacked in a crystalline structure, held together by weak forces

• YBa2Cu3O7ceramic is superconducting at 77 K (just above liquid nitrogen’s boiling point).

• The ceramic structure is called perovskite

High temperature superconductors have a complex structure containing more than one metal.

Metals with similar stacking patterns are more likely to form alloys.

Stacking Patterns:

Two or more metals coexist in structures called alloys. Copper and tin mixed together form bronze.

Effect of Carbon Content on the Properties of Steel

Carbon Content (%) Designation Properties Used to Make

0.05 - 0.19 Low Carbon Malleable, ductile Nails, cables

0.20 - 0.49 Medium Carbon High strength Construction girders

0.5 - 3.0 High Carbon Hard but brittle Cutting tools

Composition affects properties.