Urea (NH2)2CO carries amine (ammonia) generated by the catabolism of amino acids. Assume the natural abundance of 14N is 100%. Citrulline (Exam Images Sheet) is synthesized with 15N in both nitrogen atoms (assume 100%). The citrulline enters into the urea cycle. Approximately what percentage of nitrogen in the urea produced in one turn of the cycle contains a 15N, assuming the naturally occurring nitrogen isotope is 100% 14N?

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

lol idk man i guess u gotta ask bill nye the science guy

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.