The elementals of the Prayer are Five :

The elementals of the Prayer are Five :

Intention (Niyyat)
Takbiratul Ehram
Standing before the Ruku'
Ruku'
Two Sajdah in every Rak'at.

Any addition made to these elemental (Rukni) acts, intentionally, will render the prayers void. If the addition is done by mistake, the prayers does not become void except when a Ruku' is added, or more than two Sajdah are offered in one Rak'at.