1. why does the atomic model keep changing? 2. what subatomic particles of an atom are in the nucleus? 3. where are the electrons located? 4. draw an atomic model below. it should contain 4 levels with full shells. 5. how many valence electrons does iron (fe) have? how do you know?

Atomic model keep changing because the electrons around the nucleus are not fixed and they keeps rotating or changing their position in valence orbits around the nucleus. In one moment they are present on one side of the nucleus and at very next moment they will be on the other side due to their continuous rotation. so, that is why atomic models keep changing.

"Neutrons and Protons"

In the atomic nucleus, there are two main types of subatomic particles present namely as neutrons and protons. As their name implies the neutrons are the neutral particles and they possess no charges while protons are positively charged particles in contrast with electrons.

Electrons are located outside the nucleus in the valence orbits or shells. Electrons keep rotating around the central nucleus and possess negative charge with a comparison to the nucleus having a positive charge.

The atomic number of iron is 26. It means that iron contain 26 valence electrons. These electrons are arranged in different valence orbits where they keep rotating around central nucleus.

Here is a model of atom contain almost 4 levels with full electrons.

Model is given in attachments.

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