Answer: The missing coefficient is 2.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

As in the products, there are 2 atoms of sodium, thus there will be 2 atoms of of sodium in the reactant as well. This will balance the number of hydrogen and oxygen atoms as well.
Thus the missing coefficient is 2.
Hello.
The answer i believe would be sodium.
Have a great day.
Answer:
ZnS
Explanation:
1. Number of Zn atoms
4 internal atoms = 4 Zn atoms
2. Number of S atoms
8 corners × ⅛ S atom/corner + 6 faces × ½ S atom/face = 1 S atom + 3 S atoms = 4 S atoms
3. Empirical formula
The atomic ratio is
4Zn:4S = 1Zn:1S
The empirical formula is ZnS.