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The first step is to look at the set of valences and unpaired electrons.
All electrons unpaired are valence electrons. However, the valence electrons of all kinds need to be paired. Have you got this? Okay, let’s move on to the next stage of everything.
Unpaired electrons are the electrons within an orbital, which isolating, whereas the electrons in valence are simply electrons located inside the outermost layer inside an atom.
For example, an atom has the electronic configuration 1s2,2s2,2p6,3s1
. Here is the electron inside the 3s1 orbital contains also the valence as well as the single electron. What happens if we added an additional electron to the electron (just suppose we could do it). Then, the configuration will alter in the previous orbital in a way that it would become 3s2 . The electron now consists of the valence electron, but it is not unpaired. The concept can be further developed in many different ways however this is the principle that is at the heart of it.