Elements known to and used by ancient civilizations (e.g., Gold, Copper).
Produced primarily through human activity or nuclear synthesis.
Metals with high density, atomic weight, or atomic number, often toxic.
Metals with relatively low density (typically less than 5 g/cm³).
Elements occurring in nature as a single stable isotope.
Found in nature in its metallic form, either pure or as an alloy.
Formed through natural processes without human intervention.
Elements that are resistant to corrosion and oxidation in moist air.
Six transition metal elements (Ru, Rh, Pd, Os, Ir, Pt) clustered together in the d-block.
Emitting radiation as a result of nuclear decay.
Set of seventeen elements including the lanthanoids plus scandium and yttrium.
Metals that are extraordinarily resistant to heat and wear.
Material with electrical conductivity between that of a conductor and an insulator.
Having at least one isotope that does not undergo radioactive decay.
Specifically created in laboratory or nuclear reactors, not found naturally on Earth.
Essential or strictly associated with biological life processes.
Qualitative properties and descriptors associated with chemical elements.