Apologies accepted. Yes Malina, it was an interesting question.
What I need to ask you, is do you know about electrons? If you do then you will know that elements like iron are made up of atoms. Each atom of iron has a nucleus of protons (positively charged particles, 26) and neutrons (uncharged particles, 30) and surrounding the nucleus are the electrons (26 negatively charged particles). It’s the way the electrons behave that makes thing interesting. In normal elements like carbon, silicon and sulphur all the electrons are ‘tied’ to the nucleus. They cannot leave the nucleus. In the metallic elements some of the electrons are ‘tied’ but the others are free to move away from the nucleus. This is why metals can conduct electricity (which is the movement of electrons along a metallic wire). It is the free electrons which dictate whether an element is magnetic or not.
Still with me? Hope so – if not you could ask another question.
The electrons themselves are like small magnets and some of them ‘pair up’ as magnets can do. For some elements who have an odd number of free electrons you end up with a lot of free electrons for the others you get complete pairing. See below for a pairing image.
A metal is classified as ferromagnetic (very magnetic) if it has a lot of unpaired free electrons. iron and nickel are two examples.
When the iron atom begins to combine with other elements to form your hemoglobin there is further pairing of electrons between the iron atoms and the things it is combining with so it loses it’s magnetism.
That was a lot to understand. Hope you have managed.