When examining a periodic table where each element has three numbers listed beneath its symbol, which of the following values typically represents the atomic radius?

• A. The value given in picometers (pm)
• B. The value given in electrons per atom
• C. The value given in kilojoules per mole (kJ/mol)
• D. The value given in grams per mole (g/mol)

Answer: (A)

Verified step by step guidance

1. Understand that the atomic radius is a measure of the size of an atom, typically expressed as the distance from the nucleus to the outer boundary of the electron cloud.
2. Recognize that atomic radius is usually given in units of length, and the common unit used in chemistry for atomic radius is picometers (pm), which is a measure of distance on the atomic scale.
3. Identify that the other units listed—electrons per atom, kilojoules per mole (kJ/mol), and grams per mole (g/mol)—represent different properties: electrons per atom relates to the number of electrons, kJ/mol relates to energy such as bond energy or ionization energy, and g/mol relates to molar mass.
4. Conclude that the value representing atomic radius on a periodic table is the one given in picometers (pm), as it directly corresponds to a length measurement appropriate for atomic size.
5. Therefore, when you see three numbers under an element symbol, the number with units in picometers (pm) is the atomic radius.