Which statement is true for all atoms that are anions, that is, negatively charged ions?

Introduction / Context:
This question again focuses on the basic definition of an anion in atomic chemistry. An anion is a negatively charged ion, formed when a neutral atom gains one or more electrons. Understanding the relationship between the numbers of protons and electrons in ions is essential for predicting ionic charges and writing correct chemical formulas for ionic compounds.

Given Data / Assumptions:

• Protons have positive charge and are located in the nucleus.
• Electrons have negative charge and move around the nucleus.
• A neutral atom has equal numbers of protons and electrons.
• An anion must have a net negative charge.
• Neutrons are neutral and do not affect the charge.

Concept / Approach:
The charge on an ion is determined by subtracting the number of electrons from the number of protons. For a neutral atom, this difference is zero because the numbers are equal. For an anion with charge minus one, there is one more electron than proton. For charge minus two, there are two more electrons than protons, and so on. This means that for any anion, regardless of element or charge magnitude, the number of electrons must exceed the number of protons. This property is true for all anions and false for cations or neutral atoms.

Step-by-Step Solution:
Step 1: Write the charge formula. Net charge = number of protons minus number of electrons. Step 2: Apply to an anion. For an anion, net charge is negative, so protons minus electrons is less than zero. Step 3: Rearrange the relationship. If protons minus electrons is negative, then electrons are greater than protons. Step 4: Match with the options. Only the statement that the atom has more electrons than protons satisfies this condition.

Verification / Alternative check:
Consider common anions such as Cl-, O2-, and N3-. For chloride, there are 17 protons and 18 electrons. For oxide, there are 8 protons and 10 electrons. For nitride, there are 7 protons and 10 electrons. Each case shows that the electrons outnumber the protons by an amount equal to the magnitude of the negative charge. This consistent pattern across many different anions confirms that having more electrons than protons is the defining property.

Why Other Options Are Wrong:
Option B: More protons than electrons would yield a positive charge, which describes a cation, not an anion. Option C: Equal numbers of protons and electrons correspond to a neutral atom with zero net charge. Option D: All of the above cannot be correct because the statements contradict each other; only one can describe anions.

Common Pitfalls:
Students may mix up anions and cations or rely only on the plus or minus sign without understanding the underlying particle counts. Another mistake is to bring neutrons into the charge calculation, even though neutrons are neutral. A reliable approach is to remember that anions are formed by gaining electrons, so the number of electrons becomes greater than the number of protons.

Final Answer:
For all anions, it is true that the atom has more electrons than protons.