Based on relative bond strengths, classify these reactions as endothermic (energy absorbed) or exothermic (energy released)
endothermic
b2+c2--> 2bc
a+bc--> ab+c

exothermic
ab+c--> ac+b
a2+c2--> 2ac
a2+b2--> 2ab

Exothermic reaction is a chemical reaction that releases energy. This reaction releases heat energy or light . In an endotermic reaction energy is used. Enthaply is the heat energy change , delta H. If the sum of the enthalpies of the reactans is greater than the products the reaction is exothermic. If the products side has a larger enthaply than the process is endothermic. So, if delta H is negative then the process is exothermic. If delta H is positive, than the process is endothermic. Exothermic are: A+BC -> AB+C A2+B2 -> 2AB Endothermic are:AB+C -> AC+B A2 + C2 -> 2AC B2+C2 -> 2BC

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -