At room temperature, h2o is liquid, while h2s is a gas. both oxygen and sulfur have six electrons in their valence shells. what characteristic best explains the difference in properties?

               Intermolecular Forces

Explanation:

                   Both H₂O and H₂S are almost same in geometry. The only property which makes H₂O a liquid and H₂S a gas at room temperature is the type of intermolecular interactions among the molecules of these molecules.

                   As cleared from physical state it is demonstrated that H₂O molecules are having stronger Intermolecular forces as compared to H₂S. These forces are known as Hydrogen Bond Interactions. Hydrogen bonding occur between molecules having highly Electronegative atoms like Fluorine, Oxygen and Nitrogen respectively. Hence, the hydrogen atom attached to oxygen atom in H₂O becomes partially positive and make hydrogen bond with the oxygen atom of next molecules's oxygen atom.

                       On the other hand Sulfur being less electronegative than Oxygen fails to develop hydrogen bonding interaction resulting in weak intermolecular forces.