A reaction vessel that is completely sealed and the Earth would be my answers. This is because the matter inside of these systems is not exchanged anywhere but inside itself. (the glass flask could count, but the not insulated thing might be why it doesn’t count)
Answer:
Magnesium, strontium, and barium belong to group 2A of the periodic table.
Answer:
Electrons are found in shells or orbitals that surround the nucleus of an atom
Explanation:
1. Dmitri created groups of 3
2. John Newlands arranged the elements
3. Antoine Lavoisier divided them into catagories
4. Johann used patterns
hope this helped :)
