The answer is D. I did that and i got it right.
        
                    
             
        
        
        
Element   Atomic Number	Valency
Valency of Hydrogen	1	1
Valency of Helium	2	0
Valency of Lithium	3	1
Valency of Beryllium	4	2
Valency of Boron	5	3
Valency of Carbon	6	4
Valency of Nitrogen	7	3
Valency of Oxygen	8	2
Valency of Fluorine	9	1
Valency of Neon	10	0
Valency of Sodium (Na)	11	1
Valency of Magnesium (Mg)	12	2
Valency of Aluminium	13	3
Valency of Silicon	14	4
Valency of Phosphorus	15	3
Valency of Sulphur	16	2
Valency of Chlorine	17	1
Valency of Argon	18	0
Valency of Potassium (K)	19	1
Valency of Calcium	20	2
Valency of Scandium	21	3
Valency of Titanium	22	4
Valency of Vanadium	23	5,4
Valency of Chromium	24	2
Valency of Manganese	25	7, 4, 2
Valency of Iron (Fe)	26	2, 3
Valency of Cobalt	27	3, 2
Valency of Nickel	28	2
Valency of Copper (Cu)	29	2, 1
Valency of Zinc	30	2
 
        
             
        
        
        
<span>I believe that its 
Cu</span>
        
             
        
        
        
Answer:
Mass: 981.0 g
Density: 5.61 g/cm^3
Hardness: = 2.5 - 3
Unknown material: Chalcocite
Explanation: