Answer:
b. contains only valence electrons.
Explanation:
In Lewis dot diagram valence electrons are shown by the dots around the symbol of an atom. Consider the example of sodium fluoride.
Electron dot diagram is attached below.
Sodium is alkali metal and present in group one. It has one valence electron. All alkali metal form salt when react with halogens.
Sodium loses its one electron to get stable. While all halogens have seven valence electrons they need only one electron to get stable electronic configuration.
When alkali metals such as sodium react with halogen fluorine it loses its one valence electron which is accepted by fluorine and ionic bond is formed. The compound formed is called sodium fluoride.
Na + F → NaF
