The mystery element will be classified as a ; Metal
Metals as elements are good conductors of heat and electricity and are highly reactive due to number of valence electrons they posses, metals give up their valence electrons easily to achieve a full outer energy levels ( ( i.e. high reactivity levels )
Therefore a dull gray solid ( gray cast Iron ) with high level of reactivity with other elements is classified as a metal
Hence we can conclude based on the properties of the gray solid that the element is a metal.
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