Why do both nuclear fission and fusion release energy?

[Hypochondriac]

in nuclear fusion, 2 nuclei join to make one correct,
therefore there is a loss of mass and energy, that energy escapes as gamma rays etc.

but in nuclear fission, as the binding energy increases surely energy must have to come from somewhere, but apparently energy is given out?

also my revision guide says (for fission) "the average binding energy per nucleon increases so there is an overall loss in mass"
this confuses me because energy is proportional to mass, so if energy increases so does mass, not the opposite.

plus id expect fission to be the opposite of fusion but it seems they both give out energy...what am i missing/what don't i understand about this?

 

[mathman]

The nucleus with the smallest mass per nucleon is Fe56 (I may be off slightly). Therefore when light elements fuse, there is excess energy. Similarly when heavy elements fiss, there is excess energy.

 

[Hypochondriac]

ok so aslong as the resulting nucleus/nuclei are further towards iron then energy is given out

cheers