Silver is Ag from the latin Argentum
Lead is Pb from the latin Plumbum
Elements that belong to the same period which is seen horizontally in the periodic table have different properties. Elements with similar properties are seen in columns or groups. Elements in the same period have similar principal quantum number and belong to the same principal shell. Hence the answer is that t<span>hey have different properties that repeat across the next period</span>.
Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and nitrogen trifluoride (NF3).
Yo sup??
The answer to your question is option c ie
c.9
the rest 12 are under non essential as they are produced by our body itself
Hope this helps.
