Atoms consist of three basic types of particles, protons, electrons and neutrons. Neutrons and protons have approximately the same mass and in contrast to this the mass of an electron is negligible. A proton carries a positive charge, a neutron has no charge and an electron is negatively charged. Valence Electrons and Reactivity: The electrons in the outer energy level of an atom are called valence electrons. It is valence electrons that are potentially involved in chemical reactions. The number of valence electrons determines an element's reactivity, or how likely the element is to react... Show more

Atoms consist of three basic types of particles, protons, electrons and neutrons. Neutrons and protons have approximately the same mass and in contrast to this the mass of an electron is negligible. A proton carries a positive charge, a neutron has no charge and an electron is negatively charged.

Valence Electrons and Reactivity: The electrons in the outer energy level of an atom are called valence electrons. It is valence electrons that are potentially involved in chemical reactions. The number of valence electrons determines an element's reactivity, or how likely the element is to react with other elements. The number of valence electrons also determines whether the element can conduct electric current. That's because electric current is the flow of electrons. These properties vary in elements from different classes.    
- Metals such as lithium have an outer energy level that is almost empty, They “want” to give up their few valence electrons so they will have a full outer energy level. As a result, metals are very reactive and good conductors of electricity.    
- Metalloids such as boron have an outer energy level that is about half full. These elements need to gain or lose too many electrons for a full outer energy level to come about easily. As a result, these elements are not very reactive. They may be able to conduct electricity but not very well.    
- Some nonmetals, such as fluorine, have an outer energy level that is almost full. They “want” to gain electrons so they will have a full outer energy level. As a result, these nonmetals are very reactive. Because they only accept electrons and do not give them up, they do not conduct electricity.    
- Other nonmetals, such as neon, have a completely full outer energy level. Their electrons are already in the most stable arrangement possible. They are unreactive and do not conduct electricity.

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