So what exactly is a chemical bond? It is a region that forms when electrons from different atoms interact with each other. The electrons that participate in chemical bonds are the valence electrons, which are the electrons found in an atom's outermost shell. When two atoms approach each other these outer electrons interact. Electrons repel each other, yet they are attracted to the protons within atoms. The interplay of forces results in some atoms forming bonds with each other and sticking together.
The two main types of bonds formed between atoms are ionic bonds and covalent bonds. An ionic bond is formed when one atom accepts or donates one or more of its valence electrons to another atom. A covalent bond is formed when atoms share valence electrons. The atoms do not always share the electrons equally, so a polar covalent bond may be the result. When electrons are shared by two metallic atoms a metallic bond may be formed. In a covalent bond, electrons are shared between two atoms. The electrons that participate in metallic bonds may be shared between any of the metal atoms in the region.
If the electronegativity values of two atoms are:
- Metallic bonds form between two metal atoms.
- Covalent bonds form between two non-metal atoms.
- Nonpolar covalent bonds form when the electronegativity values are very similar.
- Polar covalent bonds form when the electronegativity values are a little further apart.
- Ionic bonds are formed.