Given a scientific passage and an answer, generate a question for the given answer.

Passage: Some nonmetals are very reactive, whereas others are not reactive at all. It depends on the number of electrons in their outer energy level. Answer: reactivity
The number of electrons in the outer energy level determines what property of nonmetals?

Passage: Natural gas is delivered to homes, where it is used for cooking and heating. Natural gas is also a major energy source for powering turbines to make electricity. Natural gas releases most of its energy as heat when it burns. The power plant is able to use this heat, either in the form of hot gases or steam, to spin turbines. The spinning turbines turn generators, and the generators create electricity. Answer: natural gas
What type of gas is delivered to homes to use for cooking and heating?

Passage: Charge Carried by Electrons and Protons Franklin wrote in his letters and books that he could see the effects of electric charge but did not understand what caused the phenomenon. Today we have the advantage of knowing that normal matter is made of atoms, and that atoms contain positive and negative charges, usually in equal amounts. Figure 18.5 shows a simple model of an atom with negative electrons orbiting its positive nucleus. The nucleus is positive due to the presence of positively charged protons. Nearly all charge in nature is due to electrons and protons, which are two of the. Answer: nucleus
What part of an atom is positive due to the presence of positively charged protons?