Answer:
Nitrogen
Explanation:
Nitrogen has 5 Valence Electrons.
And its atomic mass is also less than Bismuth.
There are other elements in the 5th row but this one has the lowest atomic mass compared to the others.
Answer:
Argon (Ar) is smallest element in 3rd period in periodic table.
a) The change here is that metallic iron is converted into ions and copper is deposited. This is called a displacement reaction.
b) 
is oxidised in this reaction.
c)$ \mathrm{Fe_{(s)}+ CuSO_{4(aq)} \rightarrow FeSO_{4(aq)} + Cu_{(s)}}$
The correct answer is D
a polymer is a substance made up of large molecules with repeating sub units called monomers.
A is incorrect because its a ring structure which means it cannot form the long chain that is exhibited by polymers.
B is incorrect because the double bonds will cause saturation, hence no monomer can bond to another monomer to form the large molecule.
C is incorrect because the large molecule has repeating sub-units hence only specific types of molecules can be present, and it is usually carbon and hydrogen.
