2NaN ---> 2Na + 3N2
"MN" is not a chemical symbol, but "Mn" in a chemical equation signifies the involvement of at least one manganese atom in the reaction for which the equation is valid.
The chemical equation for the reaction between a silicon atom and a chlorine molecule is: Si + Cl2 → SiCl4
Balanced equation
Balanced
The chemical equation for mercury(II) oxide is HgO. It is composed of one mercury (Hg) atom and one oxygen (O) atom.
An atom in an equaton is only the symbol of this element, not a molecule.
The subscript denotes how much of that atom is in the molecule.
a balanced equation has equal numbers of each type of atom on each side of the equation.
Balanced
A coefficient.
I'm assuming you mean water; which is H2O (2 hydrogen and 1 oxygen atom)
The laws of conservation of mass and of numbers of each type of atom.