[georgec_b]

What is the equation for the reaction of ammonia and sulphuric acid?
I've seen it written in different ways:

2NH₃ + H₂SO₄ > 2NH₄^{+ 2-}SO₄

2NH₃ + H₂SO₄ > (NH₄⁺)₂ SO₄^2-

and...
2NH₃ + H₂SO₄ > 2NH₄⁺ + SO₄^2-

[Borek]

I would say - all are wrong, although they all touch the same concept.

First of all - you have to decide, whether you are interested in molecular, ionic, or net ionic version of the equation. In the first case no charges should be written. In the second and third - sulfuric acid on the LHS should be dissociated.