That’s a really interesting one! I’m not sure we definitively know the answer to that question, but I guess it’s likely to be one of the common metals like copper or iron, or maybe even gold. Humans have been using these elements for thousands of years for things like tools, weapons and jewellery, so they’re probably the ones that we’ve definitely known about for the longest.
Great question! I believe the first periodic table was published in 1869 by a scientist called Dmitri Mendeleev – this is the guy who gets most of the credit for the periodic table even though he build on the work of other scientists before him. The first elements to be known to man were metals such as gold, silver, copper, iron, lead, tin, mercury, sulfur, and carbon. As for the periodic table, Hydrogen has the atomic number 1 so that would suggest that maybe this was the first element to be put on it? Although it’s hard to tell because the periodic table was published as a whole document with lots of different elements so it’s difficult to tell exactly which one came first…especially for someone like me who isn’t a physicist!