the 7 notes over the 5 chord (notes in the 5 chord: 5, 7 & 2)

note    tension
5       lowest (it's in the chord)
7       lowest (it's in the chord)
2       lowest (it's in the chord)
4       low (it's in a commonly used chord, called the 5 seventh chord)
6       medium
3       medium
1       very high