Objection 1. It would seem that the whole Christ was not in hell. For Christ's body is one of His parts. But His body was not in hell. Therefore, the whole Christ was not in hell.
Objection 2. Further, nothing can be termed whole when its parts are severed. But the soul and body, which are the parts of human nature, were separated at His death, as stated above (50, 3,4), and it was after death that He descended into hell. Therefore the whole (Christ) could not be in hell.
Objection 3. Further, the whole of a thing is said to be in a place when no part of it is outside such place. But there were parts of Christ outside hell; for instance, His body was in the grave, and His Godhead everywhere. Therefore the whole Christ was not in hell.
On the contrary, Augustine says (De Symbolo iii): "The whole Son is with the Father, the whole Son in heaven, on earth, in the Virgin's womb, on the Cross, in hell, in paradise, into which He brought the robber."
I answer that, It is evident from what was said in I, 31, 2, ad 4, the masculine gender is referred to the hypostasis or person, while the neuter belongs to the nature. Now in the death of Christ, although the soul was separated from the body, yet neither was separated from the Person of the Son of God, as stated above (Question 50, Article 2). Consequently, it must be affirmed that during the three days of Christ's death the whole Christ was in the tomb, because the whole Person was there through the body united with Him, and likewise He was entirely in hell, because the whole Person of Christ was there by reason of the soul united with Him, and the whole Christ was then everywhere by reason of the Divine Nature.
Reply to Objection 1. The body which was then in the grave is not a part of the uncreated Person, but of the assumed nature. Consequently, the fact of Christ's body not being in hell does not prevent the whole Christ from being there: but proves that not everything appertaining to human nature was there.
Reply to Objection 2. The whole human nature is made up of the united soul and body; not so the Divine Person. Consequently when death severed the union of the soul with the body, the whole Christ remained, but His whole human nature did not remain.
Reply to Objection 3. Christ's Person is whole in each single place, but not wholly, because it is not circumscribed by any place: indeed, all places put together could not comprise His immensity; rather is it His immensity that embraces all things. But it happens in those things which are in a place corporeally and circumscriptively, that if a whole be in some place, then no part of it is outside that place. But this is not the case with God. Hence Augustine says (De Symbolo iii): "It is not according to times or places that we say that the whole Christ is everywhere, as if He were at one time whole in one place, at another time whole in another: but as being whole always and everywhere."
Source: Summa Theologica (New Advent)