Which of the following is NOT a property affected by the effective nuclear charge?

• A. Ionization energy
• B. Molar mass
• C. Atomic radius
• D. Electronegativity

Answer: (B)

Verified step by step guidance

1. Understand what effective nuclear charge (Z_eff) means: it is the net positive charge experienced by an electron in a multi-electron atom, calculated as the actual nuclear charge (number of protons) minus the shielding effect of other electrons.
2. Recognize that effective nuclear charge influences properties related to how strongly electrons are held by the nucleus, such as ionization energy (energy required to remove an electron), atomic radius (size of the atom), and electronegativity (tendency to attract electrons in a bond).
3. Analyze each property: Ionization energy increases with higher Z_eff because electrons are held more tightly; atomic radius decreases with higher Z_eff because electrons are pulled closer; electronegativity increases with higher Z_eff due to stronger attraction for bonding electrons.
4. Consider molar mass: it depends on the total mass of atoms in a mole and is determined by the number and types of atoms, not by the effective nuclear charge, so it is not affected by Z_eff.
5. Conclude that molar mass is the property NOT affected by effective nuclear charge, while ionization energy, atomic radius, and electronegativity are influenced by it.