Below is the distribution of given elements and additional elements in their respective bins.
Iron, Magnesium, Aluminium, Calcium, Chromium and Indium are classified as Metals due to their hardness, conduction of current and heat, Solid state, formation of metallic bonding and prefers to form cations e.t.c
Oxygen, Neon and Bromine are classified as non-metals. Non-metals are mostly gases except for Bromine. They are highly volatile and prefers to form anions.
Semimetals are those metals which have both properties of metals and non-metals and are also called as metalloids.
A have no potential energy
Because the formation of rust is a kind of chemistry reaction.
After chemistry reaction, compound with new properties is produced.
Of course, color is one of the new properties.
For example, if you put iron in colorless acid solution, a green solution is made.
This kind of chemisty reaction differs from physical reaction, for example, pigment with one color dissolves in liquid, a liquid with same color is made.