In basic atomic theory, anions are negatively charged ions. Anions are formed by which of the following processes?

Introduction / Context:
This question checks your knowledge of how ions are formed, especially anions. In chemistry, ions are atoms or groups of atoms that carry an electric charge due to an imbalance between numbers of protons and electrons. Learning the difference between cations and anions, and how each is formed, is essential for understanding ionic bonding and electrolysis.

Given Data / Assumptions:

• Anions are known to be negatively charged ions.
• The options describe gaining or losing electrons or neutrons.
• We assume that the starting point is a neutral atom or group of atoms.

Concept / Approach:
In a neutral atom, the number of protons equals the number of electrons, so the net charge is zero. If the atom gains extra electrons, it now has more electrons than protons, resulting in a net negative charge. Such a negatively charged ion is called an anion. Conversely, if an atom loses electrons, it has more protons than electrons and becomes a positively charged ion, called a cation. Changes in neutrons do not affect electric charge, only mass and isotopic identity.

Step-by-Step Solution:

Verification / Alternative check:
Common examples include chlorine atoms gaining one electron to form chloride ions, Cl minus, and oxygen atoms gaining two electrons to form oxide ions, O two minus. In each case the atom becomes negatively charged by adding electrons. On the other hand, metal atoms such as sodium lose electrons to form Na plus, which are cations. These familiar examples consistently show that gaining electrons leads to anions, while losing electrons leads to cations. This confirms that gaining electrons is the correct mechanism for anion formation.

Why Other Options Are Wrong:

• Losing electrons from neutral atoms: This produces positively charged cations, not anions.
• Gaining neutrons by neutral atoms: Neutrons are uncharged, so gaining them changes the mass and isotope but not the electric charge.
• Losing neutrons from neutral atoms: Again, charge remains unchanged because neutrons are neutral, so no anion is formed.
• Simultaneously gaining protons and electrons: This could keep the charge balanced depending on the numbers gained, and is not the standard simple process for forming anions.

Common Pitfalls:
Students sometimes rely on the relative size of ions to guess their formation mechanism or confuse anions and cations because both involve electron changes. An easy way to remember the difference is that anion starts with the letter a and can be associated with the word attract, since anions are attracted to the positive anode in electrolysis. They are negative because they have gained electrons. Cations, on the other hand, are positive, and you can think of the letter t in cation as a plus sign. These small memory aids help avoid confusion on exams.

Final Answer:
Anions are formed by Gaining electrons by neutral atoms.