Build molecular models of maleic, fumarie, and succinic acids (optional). a. do the models show why these are not identical compounds? why or why not? . b. compare the rotation, if any, about the carbon-carbon double bonds in maleic and fumaric acids and about the corresponding carbon carbon single bond in succinic acid.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.