Consider these two sentences: "I gave him a pencil," and, "I gave a pencil to him."
Is it correct that the important part of the sentence is placed at the end? When we want to emphasize the pencil that I gave him, must we say, "I gave him a pencil?" When we want to emphasize that it is him to whom I gave a pencil, must we say, "I gave a pencil to him?"
The sentences are both grammatical, and mean the same thing. The difference between them is precisely that they are the two variants of the English Dative Alternation, also known as Dative Movement, or simply Dative.
Most though not all bitransitive verbs (verbs that can have both a direct object and an indirect object, like give) participate in the Dative Alternation, with two possible constructions:
This is already problematic in traditional school grammar, where there is widespread dissent about which one of the two NPs in each construction is really an Indirect Object and which one is a Direct Object. Clearly, in terms of form, construction (1) has an object of a preposition but no latinate "indirect object", while the order is reversed and the preposition is missing in construction (2).
The solution is to note that the constructions assign the same roles to the same NPs, so that, in both cases, there is a Source NP (Bill), a Receiver NP (her), and a Trajector NP (a pencil). Source and receiver are clear enough; a trajector is something that moves. So the subject in a dative construction of either sort is the Source, the direct object is the Trajector, and the indirect object is the Receiver. Normally source and receiver are human NPs, while the trajector is non-human.
There are complexities; either object can be passivized, for instance:
and they interact in complex ways with the movable particles of phrasal verbs:
(Passivization of these sentences is left as an exercise for the reader :)
I gave him a pencil is the normal choice. The alternative is less likely, and, as you suggest, may be used to give a different emphasis, but whether or not it is appropriate will depend on the context.
I don't think anybody would say "I gave a pencil to him".
We would reserve this arrangement of the phrase for something like: "I gave a pencil to the man sitting next to me", where the indirect object is a long phrase, or in a sentence such as: "I gave it to him", where the direct object is short.
