Organic chemical compounds as recommended by the (IUPAC)
Answer: it’s number 2 add a catalyst
Hopefully this helped :)
I think the answer is (1) Co. Because the element of Cobalt also has 2 electrons at the outer layer which is the same as Calcium. And the outer layer is an important factor which can affect the property of an element.
The answer should be E,C,F,B,A,D in that order.
