Click image to open full size
Chemical Bonding
Ionic, Covalent, and Metallic Bonds Compared
Related Tools
Related Labs
Chemical bonding explains how atoms join together to form substances with very different properties. The three major bonding types taught first in chemistry are ionic, covalent, and metallic bonding. Each type depends on how electrons are transferred, shared, or spread through a material. Understanding these patterns helps students predict melting point, conductivity, hardness, and solubility.
In ionic bonding, electrons are transferred from one atom to another, creating oppositely charged ions that attract. In covalent bonding, atoms share pairs of electrons to fill their outer energy levels. In metallic bonding, positive metal ions are held together by a mobile sea of delocalized electrons. These bonding models connect microscopic electron behavior to the large scale behavior of salts, molecules, and metals.
Key Facts
- Ionic bonding usually forms between a metal and a nonmetal by electron transfer.
- Covalent bonding usually forms between nonmetals by sharing electrons.
- Metallic bonding occurs in metals where valence electrons are delocalized throughout the solid.
- Coulomb attraction in ionic compounds can be modeled by F = kq1q2/r^2.
- The number of covalent bonds often follows the octet idea, where atoms tend toward 8 valence electrons.
- Metals conduct electricity because mobile electrons can move through the lattice.
Vocabulary
- Ion
- An ion is an atom or group of atoms with a net electric charge because electrons were gained or lost.
- Cation
- A cation is a positively charged ion formed when an atom loses one or more electrons.
- Anion
- An anion is a negatively charged ion formed when an atom gains one or more electrons.
- Delocalized electron
- A delocalized electron is an electron that is not tied to one atom or one bond and can move through a larger structure.
- Lattice
- A lattice is a repeating three dimensional arrangement of particles in a solid.
Common Mistakes to Avoid
- Assuming ionic bonds are made by sharing electrons, which is wrong because ionic bonding forms mainly by electron transfer and attraction between resulting ions.
- Thinking all compounds with two elements are ionic, which is wrong because two nonmetals usually form covalent bonds instead.
- Believing metallic bonding is just many ionic bonds, which is wrong because metals are held together by positive ions and mobile delocalized electrons rather than separate positive and negative ions.
- Using conductivity rules without considering state, which is wrong because ionic solids do not conduct well until melted or dissolved, while metals conduct as solids.
Practice Questions
- 1 Sodium transfers 1 electron to chlorine to form Na+ and Cl-. What is the charge on each ion, and what type of bond forms?
- 2 Magnesium forms Mg2+ and oxygen forms O2-. Write the simplest formula of the ionic compound formed between them.
- 3 A solid sample conducts electricity well, can be hammered into sheets, and does not dissolve as separate molecules in water. Which bonding type is most likely present, and why?