What is the chemical formula for water?

What is the chemical formula for water?

• A. H20
• B. HO2
• C. O2H
• D. H2O

Answer: (D)

Understanding how to write a chemical formula means using element symbols and subscripts to show exactly how many atoms of each element are in a molecule. Water is made of two hydrogen atoms and one oxygen atom, bonded together. That combination is written as H2O, with the subscript 2 on the hydrogen symbol to indicate two hydrogens, and no subscript on oxygen to indicate one oxygen. The standard notation uses capital letters for element symbols, so H2O is the correct, conventional way to represent water. The other strings don’t reflect the same counts or the standard way of writing formulas. HO2 would imply a different ratio (one hydrogen and two oxygens), as would O2H, which conveys the same atoms but isn’t the conventional arrangement for water. H20 isn’t the proper way to convey two hydrogens and one oxygen in chemical notation. So the correct representation is H2O.

Understanding how to write a chemical formula means using element symbols and subscripts to show exactly how many atoms of each element are in a molecule. Water is made of two hydrogen atoms and one oxygen atom, bonded together. That combination is written as H2O, with the subscript 2 on the hydrogen symbol to indicate two hydrogens, and no subscript on oxygen to indicate one oxygen. The standard notation uses capital letters for element symbols, so H2O is the correct, conventional way to represent water.

The other strings don’t reflect the same counts or the standard way of writing formulas. HO2 would imply a different ratio (one hydrogen and two oxygens), as would O2H, which conveys the same atoms but isn’t the conventional arrangement for water. H20 isn’t the proper way to convey two hydrogens and one oxygen in chemical notation. So the correct representation is H2O.