Which of the following primarily determines the size of an atom?

• A. The number of electron shells
• B. The type of chemical bonds it forms
• C. The number of neutrons in the nucleus
• D. The mass of the protons

Answer: (A)

Verified step by step guidance

1. Understand that the size of an atom, often referred to as atomic radius, is influenced by the distribution of electrons around the nucleus.
2. Recall that electrons are arranged in energy levels or shells around the nucleus, and the number of these shells affects how far the outermost electrons are from the nucleus.
3. Recognize that the more electron shells an atom has, the larger its atomic radius tends to be because the outer electrons are farther from the nucleus.
4. Consider that the number of neutrons or the mass of protons in the nucleus does not significantly affect the size of the atom, as these contribute mainly to the atom's mass, not its size.
5. Note that the type of chemical bonds an atom forms influences molecular structure but does not primarily determine the size of the isolated atom itself.