18. Investigue por qué en el bloque "d" se aplica la fórmula n-1 y en el bloque "f" n-2.

Sorry i dont understand the question can you rephase it?

The surface of the water droplet is held together by the attraction between molecules. in order for water to flow more easily into these small spaces, you need to decrease its surface tension. you can do this by adding soap, which is a surfactant (a material that decreases the surface tension of a liquid).

The internal energy of the system we can term it as total potential energy and kinetic energy. energy flows out of the surrounding from the system then we can say that the internal energy of the final state is lower than its initials. the sign of  δesystem is negative.δesystem = efinal - einitial=-ve  efinal  ∠einitial.

The answer your looking for is that both valance is 1 because they are both in the alkali group