Decomposing chemical compounds - Ease of Decomposition Someone asked me a question, that which of the following can be decomposed chemically:


Ammonia
Iron
Neon
Hydrogen
Fluorine


My Analysis: 

At first attempt I answered Ammonia but changed it to 'I can't answer'. My analysis of the question is as follows


If Fluorine (the name implies fluorine gas) is decomposed, but it will require to 242kJ/mol (bond dissociation enthalpy). So, its quite difficult that we will be able to decompose it chemically.
If Hydrogen (the name implies Hydrogen gas) is decomposed, but it will require to 435.88kJ/mol (bond dissociation enthalpy). So, its even more difficult that we will be able to decompose it chemically.
If If Ammonia (the name implies Ammonia gas) is decomposed, but it will require to 389kJ/mol (bond dissociation enthalpy). So, its significantly difficult that we will be able to decompose it chemically.
Its useless to say that we will be decomposing Iron or Neon, because they are already in elemental state.


Why I tempted to answer Ammonia: I thought about Haber's Process, and remembered that the enthalpy change of the main reaction is negative (N2+3H2=NH3), about -46.1kJ/mol; this implies that the enthalpy of the just opposite reaction is positive (Enthalpy change of NH3=N2+3H2). This made me to conclude that the reaction is not feasible, thermodynamically and therefore ammonia cannot be decomposed easily. Therefore I changed my answer to 'I can't Answer'

My Question:
I asked my friend my what is the answer, he said Ammonia. I was surprised but still confused. I have written all of my thoughts above, but neither I am able to justify my answer, nor is my friend able to understand my logic. I want your discussion and a final review of the question understanding
'
It really depends on what the definition of "decompose" is in this case. If you take the definition of "decompose" to be:


  ... to break down or cause to break down into component elements or simpler constituents


then the only option would be ammonia because the others are elements whereas ammonia is a compound which can be broken down into elemental Hydrogen and Nitrogen by the Haber Process. The energetics is not of concern in this case.