Why are fluorine elements more similar to bromine than neon?

The chemical properties of an element are largely determined by the number of valence or outer shell electrons it has. In general, elements will react to obtain a stable octet, meaning 8 valence electrons. Neon already has 8 electrons and so is largely chemically inert. Fluorine and Bromine each have 7 valence electrons, giving them somewhat similar chemical properties. Both are highly reactive.