Answer the following question given this paragraph: 

Pure elements with a high metallic character, meaning those that have chemical properties most similar to properties of metals, are generally very reactive. Metals tend to lose electrons in chemical reactions, as indicated by their low ionization energies. Within a compound, metal atoms have a relatively low attraction to shared electrons, as indicated by their low electronegativity values. By following the trend summary in Figure below , you can see that the most reactive metals would reside in the lower left portion of the periodic table. The most reactive metal that occurs naturally in reasonable quantities is cesium, which is always found in nature as a compound, never as a free element. It reacts explosively with water and will ignite spontaneously in air. Francium is below cesium in the alkali metal group, but it is so rare that many of its properties have never even been observed.


Q: Exemplified by cesium, which ignites spontaneously in air, pure elements with a high metallic character tend to be very what?


A:
reactive