2. Which of these has a negligible mass?
Protons Neutrons Electrons Atoms None of these
3. Which of these is a pure substance?
Blood Ocean Brass Wine Table Salt (NaCl)
4. Which of these has a positive charge?
Protons Neutrons Electrons Quarks None of these
5. How many protons in sodium-23?
11 12 23 1 0
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