Which of the following factors primarily determines the atomic radius of an atom?

• A. The type of chemical bonds the atom forms
• B. The temperature and pressure at which the atom exists
• C. The number of electron shells and the effective nuclear charge
• D. The atomic mass and density of the atom

Answer: (C)

Verified step by step guidance

1. Understand that the atomic radius is the measure of the size of an atom, typically the distance from the nucleus to the outer boundary of the electron cloud.
2. Recognize that the atomic radius is primarily influenced by the number of electron shells (energy levels) because more shells mean electrons are farther from the nucleus, increasing the size of the atom.
3. Consider the effective nuclear charge (Z_eff), which is the net positive charge experienced by electrons after accounting for shielding by inner electrons; a higher Z_eff pulls electrons closer, decreasing the atomic radius.
4. Note that while factors like chemical bonding, temperature, pressure, atomic mass, and density can affect atomic behavior or physical state, they do not primarily determine the intrinsic atomic radius.
5. Conclude that the atomic radius depends mainly on the balance between the number of electron shells (which tends to increase size) and the effective nuclear charge (which tends to decrease size).