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

Passage: By losing an electron, the sodium atom becomes a sodium ion. It now has one less electron than protons, giving it a charge of +1. Positive ions such as sodium are given the same name as the element. The chemical symbol has a plus sign to distinguish the ion from an atom of the element. The symbol for a sodium ion is Na + . Answer: becomes sodium ion
What happens when a sodium atom loses an electron?

Passage: Some chemical reactions can occur in only one direction. These reactions are called irreversible reactions. The reactants can change to the products, but the products cannot change back to the reactants. These reactions are like making a cake. The ingredients of a cakesuch as eggs and flourare the reactants. They are mixed together and baked to form the cake, which is the product (see Figure below ). The cake can't be "unbaked" and "unmixed" to change it back to the raw eggs, flour, and other ingredients. So making a cake is irreversible. Answer: irreversible
What are reactions that can occur only in one direction called?

Passage: For decades Pluto was a planet. But even then, scientists knew it was an unusual planet. The other outer planets are all gas giants. Pluto is small, icy and rocky. With a diameter of about 2400 kilometers, it has only about 1/5 the mass of Earth's Moon. The other planets orbit in a plane. Pluto's orbit is tilted. The shape of the orbit is like a long, narrow ellipse. Pluto's orbit is so elliptical that sometimes it is inside the orbit of Neptune. Answer: neptune
Pluto's orbit is so elliptical that sometimes it is inside the orbit of which planet?