Calculate the change in the entropies of the system and the surroundings, and the total change in entropy, when the volume of a sample of argon gas of mass 21 g at 298 k and 1.50 bar increases from 1.20 dm3 to 4.60 dm3 in
(a) an isothermal reversible expansion,
(b) an isothermal irreversible expansion against pex = 0, and
(c) an adiabatic reversible expansion.

the answer is barium and copper bromide

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.