What is a very long molecule that has chemicals in a special order?

It will be a polymer

A polymer is a macromolecule which is obtained by repetitive combination of small molecules known as monomers.

When these monomers are combined in repetitive manner they form a long chain of small monomers or a very long molecule

Now in case of polymer also there is formation of bond between monomers which is possible only if they combine in a definite or special order.

Now here the answer can be very specific like

a) bio polymer : example : DNA , RNA , Protein, starch, cellulose

b) synthetic polymer: polyethylene, PVC

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

i do not get it   at all