If zodiac signs where chemical elements/compounds...Aries = Hydrogen (H)
Hydrogen comes first in the periodic table of elements, with an atomic weight of 1. "It's also the most abundant chemical substance". ( Wikipedia)
It's the most flammable gas in the univers - exists in the sun/stars flares, and can result into a big combustion if its concentration in air reached a certain peak.
While reacting with ions, it becomes positively charged , and forms acids ... scorchingly hot , just like Aries
Taurus = Carbon (C)
It's one of the three elements that forms organic compounds. The carbon in these compounds forms a very long,stable and strong bonds. Diamond( carbon atoms formed in a crystalline structure ) is extremely rigid and currently the hardest material known. And ooh it's one of the most beautiful crystals
Gemini = Dioxygen ( O2 )
Dioxygen consists of two atoms of oxygen, without the other atom it becomes very unstable. Dioxygen is the only oxidizer and without it , no fire can be ignited. It's very reactive and it doesn't stay for long on the earth surface. It has an electronegativity that allows it to form bonds with any other element ... so Gemini
Libra = Water (H2O)
Water is the balance between Acids and Alkalies, has a pH scale of 7 ( out of 14 )while reacting with acids ,it acts as an alkaline and can turn it into a neutral solution. And when it reacts with alkalies it acts as acid and does the same. Water is capable of dissolving many elements and other compounds. Water is the main reason of creating a rainbow; the water drops acts as a crystal shattering the light into its main elemental colors.
Scorpio = Iron/Ferrum (Fe)
An element belongs to group #8 - also adding its atomic number (26) will give 8, very rigid and strong element.Black - silver in color. Not highly reactive but When reacting under inconvenient circumstances can turn into Iron Oxide- known also as rust. Found in vital human organs. It bonds with other chemical compounds to form the human blood. Iron is highly toxic and can cause death if it exists excessively in our bodies.
Sagittarius = Fluorine(F)
a pale yellowish gas with an atomic number of 9. It's the most reactive element in the periodic table- soo saggy! Its two outer electrons are very distant from each other. It forms bonds with elements very easy and fast, however most of them are weak bonds.
Aquarius = Luminol (C8H7N3O2)
A complex compound, that forms a chemical substance used widely in investigations/forensic science. When reacting with an oxidizing factor it radiates a strikingly blue-ish glow http://www.lambdasyn.org/synfiles/pictures/highres/luminol02-big.jpg
Pisces = Argon (Ar)
Is a noble -meaning not as highly active- nontoxic gas. Its spectral line goes between blue to light violet. It only glows in a field with a high potential electric energy. "Argon in greek means lazy or inactive one.(Wiki)
Cancer = Lactose (C12H22O11)
Is an organic sugar found in mammals' milk - also known as the milk sugar. It contains an enzyme called lactase, that helps digest the food easily. It 's widely used in food industry, also can be used to cut off heroine addiction.
Leo = <you guessed it right !!> Gold (Ag)
A metal that has a bright yellowish color. Not easy to react or bond with other elements, nor difficult to mix it with other materials too. Unlike other metals it resists any rusting/oxidizing factors and maintain its glow for long
Virgo = mercury (Hg)
A silvery metal liquid with a high viscosity. Relatively it's bad heat/electricity conductor. "In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health."- of course it was one hell of a terrible thought, since it's highly toxic
Mercury is widely used in medicine today : medical equipments like thermometers and healthcare like vaccines. "The symbol for the planet Mercury (☿ has been used since ancient times to represent the element " (wiki).