Why is energy released in order to react two atoms to form a compound?
For instance the reaction between sodium metal and chlorine gas is highly exothermic and produces NaCl(s). Meanwhile when an atom loses an electron, it will be endothermic.
Can someone try to explain this as best as possible? Thanks!
2 answers
http://wps.prenhall.com/wps/media/objects/3311/3391006/blb0802.html
It's a matter of total energy gain/loss around the "circuit" making up the reaction. It takes energy to ionize a Na atom. It takes energy to dissociate a Cl2 molecule. Energy is released when the Cl atom gains an electron to become a chloride ion. But huge amounts of energy are released when the Na ion and chloride ion come together. There is the force of attraction between the positive and negative ion to make a more stable compound molecule of NaCl, the crystal lattice that is formed is much more stable than the individual molecules, etc. The bottom line is that the NaCl crystal is lower in energy than the Na atom and chlorine molecules. Just as water flows down hill, from higher places to lower places, chemical systems move from higher energy levels to lower energy levels. This is the essence of it. I've said a few things that might not stand up in court but I hope this helps.
1 answer