較活的元素是否較遲被發現?

Yes, the more reactive the element, the latter the time it was discovered.

Take metals as examples.

The unreactive metals such as gold and silver, they were discovered in ancient time as they remain as element in the earth. Extraction of these metals are quite easy, it only requires physical methods.

The more reactive one such as copper, they were also discovered in ancient time, but probably later than that of gold or silver, as extraction of pure copper requires the heating between carbon and copper ore.
2CuO (s) + C (s) → 2Cu (s) + CO2 (g)

The more reactive one such as iron require stronger heating between iron ore and carbon, that's why the iron age comes later than copper age in human history.

The most reactive one such as calcium, sodium, extraction of those metals require electrolysis of molten ore, which is a quite advance technology, so most of them are found in the recent hundred years.

The reactivity of metals:

圖片參考：http://www.wpbschoolhouse.btinternet.co.uk/page03/3_33reactivity/reactivityfinal1.gif


圖片參考：http://www.wpbschoolhouse.btinternet.co.uk/page12/gifs/ReactivitySeriesList.gif



So, the lower in the reactivity series, the less reactive the metal is, and vice versa.


Same theory is applicable for non-metals. Unreactive non-metals such as carbon and sulphur were discovered in ancient times.
But the most reactive one such as fluorine and chlorine, they were found in these hundred years.

yes.
because more reactive elements,easier to have reaction with others.Since they have different appearances,it is difficult to find them.So,we need more time to find them.