How many valence electrons are in an atom of Iron

Answer: A neutral atom of Iron has two valence electrons located in the fourth energy level. 

Properties of Iron. Source

As mentioned above, Iron contains two valence electrons located in the fourth energy level. Iron is technically part of Group 8 in the Periodic Table but it is typically just grouped in with many of the other "transition metals." A Bohr model for Iron can be viewed below which confirms the presence of two electrons within the valence shell:

Bohr Model of Iron with different orbital shells labelled. Source

The reason for the low number of valence electrons in the fourth shell is due to the filling up of the d-shell in the third energy level before more electrons are placed into the fourth energy level (in either the p, d or f sublevels). Iron's entire valence shell consists of two electrons in the s subshell, the same number as many other elements in the fourth row including Potassium, Calcium and Zinc. 

Iron Orbital Notation. Source

Iron as a transition metal with extra electrons in the d-orbital of the third energy level oftentimes participates in metallic bonding with other iron atoms. Metallic bonding a property in many other transition metals because the large number of electrons in the third energy level shield the positive nucleus from the two outer valence electrons. This makes them very mobile between all of the different atoms within the structure and makes these metals excellent conductors of electricity.

Metallic Bonding in an Iron Compound. Source

Iron was one of the few elements known in its pure form to the ancient world. Due to the ease with which Iron corrodes, it was originally a rare choice for tools and weapons. However, as the technology and knowledge associated with Iron metallurgy progressed, its use picked up considerably in all of the ancient civilizations. The forged items were utilized for a wide variety of applications including agriculture, construction and warfare. 

Sources:

https://pubchem.ncbi.nlm.nih.gov/compound/Iron