Question

how do you calculate mass number? protons + neutrons neutrons + protons + electrons mass x percent protons + electrons

Explanation:

Step1: Recall mass number definition

Mass number is sum of protons and neutrons in an atom.

Step2: Analyze each option

• Option 1: Protons + Neutrons. Correct as per definition.
• Option 2: Neutrons + Protons + Electrons. Electrons have negligible mass, not included.
• Option 3: Mass × percent. Incorrect, not relevant formula.
• Option 4: Protons + Electrons. Electrons' mass ignored, wrong.

Answer:

Protons + Neutrons