Single replacement because only one letter is being switched out in the reaction
So you need to put numbers before each compound to make sure there are the exact same number of elements on each side. If you put a 4 before NH4 there are 4 Nitrogen and now 16 hydrogen. I just played around with numbers and guessed until I got them even.
1) For example, sodium oxide (Na₂O).
One one molecule of sodium oxide has one sodium atome (Na) and two oxygen atoms (O).
The subscript after element shows the number of elements in a molecule.
2) Yes, it possible for two different compounds to be made from the exact same two elements.
This are isomers, same molecular formula, but different arrangements of atoms.
For example, n-butane (C₄H₁₀) and 2-methylpropane (C₄H₁₀).
3) There are large number of compounds in this world, around 40 millions.
