(4) You notice a thin film of insoluble solid floating on the surface of the pool's water. What type of reaction do you think caused this? According to this type of reaction, what would floating film be called? *

A double-replacement precipitation reaction.

The floating film is called a precipitate.

Explanation:

precipitation reaction is a type of double-replacement reaction that occurs when two ionic compounds are dissolved in water and form a new ionic compound that does not dissolve; this new compound falls out of solution as a solid precipitate.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.