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. The nonmetal attracts the valence electrons from the metal, because metals have less valence electrons than nonmetals. 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 usually powdery, are very hard, don't conduct electricity as solids (but can conduct electricity by being dissolved in water or by being melted), and have high melting points.
Definition: A bond that is formed by two atoms when they share electrons.
A covalent bond is usually formed between two nonmetals. Since these atoms both have a high number of valence electrons, they both attract electrons. If the difference between the electronegativities is between 0-0.3, then the bond is non-polar covalent, and they share the electrons equally. If the difference between the electronegativities is between 0.3-1.7, then the bond is polar covalent, and they share the electrons unequally.Anything that results in a difference of electronegativities that is over 1.7 is an ionic bond. Substances that are formed by covalent bonds are usually powdery, have a low melting point, and don't conduct electricity.
Definition: A bond that is formed between metal atoms and the surrounding electrons.
A metallic bond is formed between two metals. Since metals have very few valence electrons, the outer electrons become easier to transfer. 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 usually shiny, and are easier to melt than substances formed by ionic bonds, but have higher melting points than substances formed by covalent bonds. They also conduct electricity very well, and don't dissolve in water.