Which of the following elements has eight valence electrons?
a. argon
b. beryllium
c. chromium
d. oxygen

Option (a) is the correct answer.

Explanation:

Atomic number of argon is 18 and its electronic configuration is  . Hence, there are eight electrons present in the outermost shell of argon.

Atomic number of beryllium is 4 and its electronic configuration is . Only 2 electrons are present in its outermost shell.

Atomic number of chromium is 24 with electronic configuration . There are only 5 valence electrons present in it.

Atomic number of oxygen is 8 and its electronic configuration is . Hence, there are only 6 electrons present in its valence shell.

Thus, we can conclude that out of the given options argon element has eight valence electrons.

nuclear fission produces elements that are heavier than helium.

the elements that are used in nuclear fission and their products are much heavier than helium.