How do the properties of a compound like h2o or nacl illustrate the concept of emergent properties?

Answer and explanation;

Na - metal

Cl - poisonous gas

NaCl - cyrstaline solid that is edible

An emergent property is a property which a collection or complex system has, but which the individual members do not.

Water emergent properties: cohesion & adhesion, versatile solvent, temperature moderation, freezing.

The properties of a compound can be very different from the properties of the elements that make them, for example, Sodium is an explosive metal, and Chlorine is a toxic gas, however, sodium chloride is a Delicious table salt!