In the table of mendeleev, the lines feature the elements in increasing order of atomic mass<span>.
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hope this helps!
Answer:
Pretty sure its B sorry if im wrong
Explanation:
They are very stable (not reactive).
This is because their outer shell has a total of 8 valence electrons. All elements strive to get towards a full outer shell, but since these elements already have a full outer shell, they are fairly unreactive.
