The half-life of uranium-235 is 700 million years. If there are 2000 g of uranium-235 in the original sample, what happens after 2100 million years have passed? Select all that apply. A.
One half-life has passed.

B.
500 g of the original sample remains.

C.
Two half-lives have passed.

D.
250 g of the original sample remains.

E.
125 g of the original sample remains.

F.
Three half-lives have passed.

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.

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.