Early wheels were simple wooden disks with a hole for the axle. In the early Roman empire, most horse-carts used a design featuring two chords across the wheel. The spoked wheel was invented much more recently, and allowed the construction of lighter and swifter vehicles.
Chromium(III) sulfide. Chromium(III) Sulfide is the inorganic compound with the formula Cr2S3. It is a brown-black solid. Chromium sulfides are usually nonstoichiometric compounds, with formulas ranging from CrS to Cr0.67S (corresponding to Cr2S3). Preparation.
indium Ge4+ germanium As3-arsenide selenide Se2-bromide Br-krypton Kr telluride Te2-Po2+ polonium(II) polonium(IV) Po4+ iodide I-xenon Xe astatide At-radon Ra hydride H-1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18