Co2 concentrations in the atmosphere are stable around 408 ppm (parts per million), which translates to approximately 1016 molecules cm-3 . what is the mass concentration of co2 in units of μg m-3 ? given the annual rate of increase of co2 of 1.6 ppm yr-1 , what is the projected co2 concentration in 2100 in units of ‘ppm’ and ‘μg m-3 ’? hint: assume an air density of 2.4×1019 molecules cm-3 .

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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.