Copper - Cu is the answer
B I think sorry if I’m wrong
Double bonds are not formed by chlorine. To complete its octet, oxygen requires two bonds (two single bonds or one double bond) and two lone pairs.
Chlorine can only form single bonds unless, for instance, it is bonded to oxygen (ClO3H), in which case, the oxygen forces chlorine to form double bonds.
The chemical element chlorine has the atomic number 17 and the symbol Cl. The second-lightest halogen, fluorine is situated between bromine and fluorine in the periodic table and has most of its features in the middle. At room temperature, chlorine is a gas that is yellow-green.
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The bond that exist between two oxygen atoms is
called a double covalent bond. This bond involves the sharing of four electrons
to obtain a more stable structure. This type of bond is much stronger than the
single covalent bond. They are much harder to break.
Answer:
≈ 2.74 mol 
(I rounded to 3 sig figs because the starting amount has 3 sig figs.)
Explanation:
2.73736313184 mol
≈ 2.74 mol 
Hope this helps!