Question

multiple-choice question
the period number tells the number of _______ that an atom has.
neutral bonds
atomic radii
proton orbitals
electron shells

Explanation:

To solve this, we recall the concept of periods in the periodic table. The period number of an element corresponds to the number of electron shells (energy levels) an atom of that element has. Let's analyze each option:

• "neutral bonds": Period number has no relation to neutral bonds.
• "atomic radii": Atomic radii is a property related to size, not directly to period number in terms of counting.
• "proton orbitals": Protons are in the nucleus, and orbitals are for electrons, so this is incorrect.
• "electron shells": By definition, the period number equals the number of electron shells an atom has.

Answer:

D. electron shells