Answer: Lithium has the least mass.
Explanation: Period 2 of the Periodic Table includes the following elements:
• Carbon
• Nitrogen
• boron
• Lithium
• beryllium
• Neon
• oxygen
• fluorine
Clarification
Out of these elements, lithium has the least mass, which is 6.941 units. The element with the most mass on the other hand is neon, which has a mass of approximately 20.1797 units.
Final answer: The element in Period 2 of the Periodic Table with the least mass is lithium.
