Answer:
933.33 g/cm³
Explanation:
Density = mass / volume
Density = 2800/3 = 933.3 g/cm³. 
 
        
             
        
        
        
Answer:
7. 4H₂O
 Elements: Hydrogen, Oxygen
Number of molecules: 4
Number of elements: 8 H, 4 O
Number of Atoms: 12
Explanation:
The elements are determined by the their symbol i.e. H = hydrogen.
The number of molecules is determined by the coefficient ( the number in front of everything, in this case 4).
The number of elements is determined by the coefficient and the subscripts. Multiply the coefficient by the subscript after each element. When there is no subscript, it is equal to 1.  4H₂ = 4x2 = 8;  4O = 4x1 = 4.
The number of atoms is all the individual elements added together. 8+4 = 12.
 
        
             
        
        
        
6 sodium and 6 Bromine in 6NaBr
        
             
        
        
        
Answer:
a.the smallest building blocks of matter
Explanation:
because atoms are the smallest building blocks of matter.