Proteins are made of hundreds and thousands of polymers called Amino Acid which are attached with each other in long chains. There are 20 different types of amino acids that make up a protein
Adenine, Cytosine, Guanine, and Thymine.
The precambrian era makes up about 90% of the earths history, but there was little to no living organisms at the time other than microscopic ones. The first eukaryotes were found in the cambrian period after the precambrian period, not only that but at the end of the precambrian era in the Proterozoic era there was a mass extinction of about 70-80% of all living organisms
Answer : A metal in group 16 of the periodic table can become a chemically stable ion by gaining 2 electrons.
Explanation :
The group 16 element are oxygen, sulfur, selenium, tellurium and polonium.
The general electronic configuration of group 16 elements is, 
As we now that there are total 6 electrons in p sub-shell. So, a metal in group 16 can become a chemically stable ion by gaining 2 electrons.

Hence, a metal in group 16 of the periodic table can become a chemically stable ion by gaining 2 electrons.