The formula of hydroxide is OH- because it consists of one oxygen atom (O) covalently bonded to one hydrogen atom (H). The oxygen atom has a valence of 2, meaning it can form two covalent bonds. The hydrogen atom has a valence of 1, meaning it can form one covalent bond. When these two atoms bond, the oxygen atom shares one of its valence electrons with the hydrogen atom, and the hydrogen atom shares its valence electron with the oxygen atom. This creates a stable covalent bond between the two atoms. The resulting molecule has a negative charge because the oxygen atom has one more valence electron than the hydrogen atom. This negative charge is indicated by the - sign at the end of the formula.

Here is a more detailed explanation of the bonding in a hydroxide molecule:

* The oxygen atom has six valence electrons, which are located in its outermost electron shell.

* The hydrogen atom has one valence electron, which is also located in its outermost electron shell.

* When the oxygen and hydrogen atoms bond, the oxygen atom shares one of its valence electrons with the hydrogen atom.

* The hydrogen atom shares its valence electron with the oxygen atom.

* This creates a covalent bond between the two atoms.

* The resulting molecule has a negative charge because the oxygen atom has one more valence electron than the hydrogen atom.

The hydroxide ion is a very important molecule in chemistry. It is found in many different compounds, including water, acids, and bases. It is also essential for many biological processes, such as respiration and photosynthesis.