In chemistry, Cr OH 3 is the chemical formula for a molecule containing one atom of chromium, one atom of oxygen and three atoms of hydrogen. When written with notation as Cr(OH)3, the formula refers to the compound chromium(III) hydroxide, also known as chromic hydroxide.
If the formula contains parentheses around the OH, the number three refers to the number of atoms present, indicating three oxygen atoms and three hydrogen atoms. Without the parentheses, the three only modifies the hydrogen symbol. The two ions that make up chromium(III) hydroxide are a chromium ion with a plus three charge and a hydroxide ion with a minus one charge.