Chemical Bonds

Ionic bond:

Definition- A bond that is formed by the electrical attraction between cations and anions.


An ionic bond is usually formed between a metal and a nonmetal. When these two atoms bond together, the nonmetal attracts the electrons towards itself due to its higher electronegativity. This causes the metal to become a cation, and the nonmetal to become an anion. Since they have different charges, the cation and the anion are attracted to each other, which forms the ionic bond.


Substances that are formed by ionic bonds are powdery or granular (and have crystal-like formations), and are very hard.  They don't conduct electricity as solids, but can after being dissolved in water or after being melted. However, the melting point for these substances is very high.


An example of a substance formed by ionic bonds is NaCl (table salt)

Covalent bond:

Definition- A bond that is formed by two atoms when they share electron(s).


A covalent bond is usually formed between two nonmetals. Since these atoms both have high electronegativities, they both attract electrons. If the difference between the electronegativities is between 0-0.3, then it is said that the bond is non-polar covalent, and they share the electron(s) that are involved in bonding equally. If, however, the difference between electronegativities is between 0.3-1.7, then it is said that the bond is polar covalent, and they share the electron(s) that are involved in bonding unequally (a difference between electronegativities that is over 1.7 results in an ionic bond). A polar covalent bond results in one end of the bond being a slightly different charge than the other end.


Substances that are formed by covalent bonds are powdery or granular, are not as hard as substances formed by ionic bonds, and are easier to melt.  They usually do not conduct electricity.


An example of a substance formed by covalent bonds is C12H22O11 (sucrose sugar)

Metallic bond:

Definition- A bond that is formed between metal atoms and the surrounding electrons.


A metallic bond is formed between metals. Since metals have very few electrons in their outermost  energy levels, and have low electronegativities, the outer electrons become delocalized and flow freely through the empty orbitals of the metal atoms. These electrons no longer belong to a specific atom. The atoms and electrons become attracted to one another due to their different charges, and form a metallic bond.


Substances that are formed by metallic bonds are shiny, and are easier to melt than substances formed by ionic bonds. However, they are harder to melt than substances formed by covalent bonds. They conduct electricity well, and can't be dissolved in water.


An example of a substance formed by metallic bonds is Cu (copper)

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