Difference Between Valence Electrons and Free Electrons

Main Difference – Valence Electrons vs Free Electrons

An atom is composed of three types of subatomic particle: electrons, protons, and neutrons. Protons and neutrons are in the nucleus of the atom. Electrons are located outside the nucleus. These electrons are in continuous movement around the nucleus at certain distances. The pathways that these electrons move in are called electron shells or orbitals. One atom can have one or more orbitals. Valence electrons are the electrons that can be found in the outermost orbital of an atom. Free electrons are not bound to atoms. These electrons can be found in lattice structures. They are in free movement inside the lattice. The main difference between valence electrons and free electrons is that the number of electrons is an elemental property whereas the number of free electrons is a lattice property.

Key Areas Covered

1. What are Valence Electrons
      – Definition, Examples, Effect on the Oxidation State
2. What are Free Electrons
      – Definition, Occurrence
3. What is the Difference Between Valence Electrons and Free Electrons
      – Comparison of Key Differences

Key Terms: Atom, Atomic Number, Electrons, Free Electrons, Lattice, Metal, Neutrons, Nucleus, Orbital, Protons, Valence Electrons

What are Valence Electrons

Valence electrons are electrons present in the outermost orbitals of an atom. These are the electrons that have the least attraction towards the nucleus of an atom. This is because valence electrons are located in a long distance than other electrons of that atom.

Valence electrons are responsible for chemical reactions and chemical bonding of an atom. Since the attraction between valence electrons and the nucleus of an atom is less, valence electrons can easily be removed (than the electrons in the inner orbitals). This is important in the formation of ionic compounds and covalent compounds. By losing valence electrons, atoms can form cations. Sharing valence electrons of an atom with the valence electrons of another atom forms covalent bonds.

For s block elements and p block elements, the valence electrons are in the outermost orbital. But for transition elements, the valence electrons can be present in inner orbitals as well. This is due to the energy difference between the suborbitals. For example, the atomic number of Manganese (Mn) is 25. The electron configuration of cobalt is [Ar] 3d⁵4s². The valence electrons of cobalt should be in the 4s orbital. But there are 7 valence electrons in Mn. The electrons in the 3d orbital are also considered as valence electrons because the 3d orbital is located outside the 4s orbital (the energy of 3d is higher than the 4s orbital).

Figure 1: Valence Electrons of Carbon

The oxidation state of an atom depends on the valence electrons of that atom. Some atoms remove valence electrons in order to get stabilized. Then the oxidation state of that atom increases. Some atoms gain more electrons in the outermost orbital. Then the number of valence electrons of that atom increases. It decreases the oxidation state of the atom.

What are Free Electrons

Free electrons are electrons that are not attached to an atom. Free electrons cannot be found everywhere. This is because a lone electron is very reactive and can react with anything. But in crystal structures and metals, free electrons can be found.

Free electrons are the delocalized electrons from the lattice. In crystal structures, some electrons do not remain in their place due to crystal defects. They become free electrons that can move anywhere inside the lattice. These electrons are responsible for the conduction of heat and electricity.

Figure 2: Free Electrons in a Metal Lattice

In metals, there are free electrons between metal ions. It is a lattice of metal ions in a sea of free electrons. These free electrons can conduct heat and electricity through the metal. These free electrons can conduct an electrical current via the metal.

Difference Between Valence Electrons and Free Electrons

Definition

Valence Electrons: Valence electrons are the electrons present in the outermost orbitals of an atom.

Free Electrons: Free electrons are electrons that are not attached to an atom.

Attraction to the Nucleus

Valence Electrons: Valence electrons have less attraction towards the nucleus of an atom.

Free Electrons: Free electrons have no attraction towards the nucleus of an atom.

Chemical Bonding

Valence Electrons: Valence electrons are responsible for the chemical bonding of an atom.

Free Electrons:  Free electrons are not involved in chemical bonding.

Conduction of Heat and Electricity

Valence Electrons: Valence electrons cannot conduct heat and electricity.

Free Electrons: Free electrons are responsible for the conduction of heat and electricity.

Nature

Valence Electrons: The number of valence electrons is an elemental property.

Free Electrons: The number of free electrons is a lattice property.

Conclusion

Valence electrons are electrons that are loosely bound to an atom. Free electrons are completely unbound to any atom. Valence electrons are responsible for the chemical reactions and chemical bonding of atoms. Free electrons take part in heat and electricity conduction of a lattice structure. There are many differences between valence electrons and free electrons. The main difference is that the number of electrons is an elemental property whereas the number of free electrons is a lattice property.

References:

1. “Valence electron.” Wikipedia, Wikimedia Foundation, 29 Oct. 2017, Available here.
2. “The Free Electron.” NDT Resource center, Available here.

Image Courtesy:

1. “Carbon diagonal rule” By CK-12 Foundation (raster), Adrignola (vector) – File:High School Chemistry.pdf, page 317 (CC BY-SA 3.0) via Commons Wikimedia