Question

whats the difference between fission reactions and fussion reactions

Answer 1

Nuclear Fission and Nuclear Fusion are reactions involving the nucleus of Elements.
In nuclear fission- the nucleus of a radioactive element ,say uranium235, is split by a high energy neutron to produce Krypton 92, Barium 141 , 3 neutrons and heat energy. these 3 neutrons further acts on multiple U235, to continue the reaction chain .The heat energy produced is utilized for generating electricity and other purposes. http://en.wikipedia.org/wiki/Nuclear_fission
In fusion reaction - multiple nuclei are collided to produce a heavy nucleus, neutron and heat energy. example-colliding isotopes of Hydrogen (deuterium & tritium) ,produces helium and heat energy. Fusion reaction takes place in stars.
http://en.wikipedia.org/wiki/Nuclear_fusion energy calculation is based on mass -energy equation.....it is described in wiki pages

Answer 2

so i can conclude that fission produces elements that precede it? and fussion results in elements that come after it?

Answer 3

If you are talking about atomic number (Z) when you speak of "precede" and "come after", then the answer is yes.

Fission breaks relatively heavy atoms and the end result is a bunch of lighter atoms. Fusion combines relatively light atoms, and the end result is a heavier atom.