2. Which of these can an element have a different number of?
Protons Neutrons Electrons All of these None of these
3. Which of these is a pure substance?
Blood Ocean Brass Wine Table Salt (NaCl)
4. How many neutrons in carbon-13?
13 0 1 7 6
5. How many electrons in boron-11?
11 5 6 10 None of these
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