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.
The formula for Sulphur dioxide is: SO2. An easy way to do this for yourself, is by knowing the abbreviations of the periodic table , and the index numbers. Periodic abbreviations are easily found on google, wiki, etc. The index numbers are like this: 1. Mono 2. Di 3. Tri 4. Tetra 5. Penta 6. Hexa 7. Septa 8. Octo. You can easily find these online.