Which statements describing chemical and nuclear reactions are true? 1. the nucleus of an atom participates in a chemical reaction. 2. chemical reactions involve the rearrangement of electrons. 3. chemical reactions can produce new elements. 4. nuclear reactions require heat or an input of energy to occur. 5. isotopes of the same element behave differently in a nuclear reaction.

Answer is: 2. Chemical reactions involve the rearrangement of electrons and 5. Isotopes of the same element behave differently in a nuclear reaction.

1) The electrons of an atom participates in a chemical reaction.

2) Chemical reactions involve the rearrangement of electrons, because there is transfer, loss, gain and sharing of electrons in chemical reactions.

3) Nuclear reactions can produce new elements, because number of protons and neutrons is changed.

4) Chemical reactions require heat or an input of energy to occur, this is activation energy.

5) Isotopes of the same element behave differently in a nuclear reaction, because isotopes have different number of neutrons, so products of a nuclear reaction is different.

Chemical reactions involve the rearrangement of electrons.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.