4. which element is highly reactive: sodium, helium, or chlorine?
5. why is helium considered an unreactive element?
6. what determines an element's' chemical property?
7. list these elements in order of most reactive to least reactive: ca, c, s, and ar.
8. which elements have the same chemical properties: (na & mg), (na & ca), or (na & k)?
9. which element has the fewest valence electrons: iron, fluorine, potassium, or neon?
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