MICSP - Types of Chemical Bonds (Lesson)
Types of Chemical Bonds
Depending on the electronegativity difference between the two elements in a chemical bond electrons will either be shared between the two nuclei (covalent bonding) or the electrons will be completely transferred from one element to to another (ionic bonding). These differing chemical bonds give rise to different physical and chemical properties; some of which will be explored in later modules.
Ionic Bonding
Ionic bonding is perhaps the simplest type of bonding to understand because it simply involves the complete transfer of electrons. The driving force for this electron transfer is to ensure that each element has a noble gas electron configuration after the transfer is complete. This then results in charged ions which are attracted to each other through Coulombic attractions which are discussed further in a later lesson.
Covalent Bonding
This type of bonding occurs between elements who, although they may have some electronegativity difference, the difference is not great enough to result in the formation of ions. These elements still seek to obtain a noble gas electron configuration; however, they share electrons between nuclei as opposed to completely losing them to or gaining them from other atoms.
Metallic Bonding
Metallic bonding is a type of chemical bonding that is rarely mentioned in AP Chemistry. These bonds are formed between atoms of metallic elements such as sodium, iron, gold, etc. The nature of the bond itself gives rise to its characteristic chemical properties such as conductivity, ductility, malleability, and so on. The valence electrons of these elements are very mobile and are shared among several different nuclei and create what is referred to as a "sea of electrons". These bonds will be referenced in a later module, but will not be addressed any further here.
Spectrum of Bonding
While chemical bonds are often categorized as ionic and covalent, these terms actually describe the extremes of chemical bonding. All chemical bonds essentially fall on a spectrum between 100% pure covalent and 100% pure ionic rather than into two distinctly different groups.
IONIC BONDS |
COVALENT BONDS |
|---|---|
| Atoms that have gained or lost electrons to complete octets are attracted by electrostatic force (Coulomb's Law) | Neutral atoms share electrons in order to increase electron stability by lowering the potential energy profile. |
| Happens between ions | Happens between atoms of nonmetals |
| Become formula units of a salt | Become molecules of molecular compounds |
This spectrum can be illustrated using the difference in electronegativity values of the elements bonding. The cut-off numbers in this spectrum are arbitrary and depend on how the electronegativity value was determined. In other words, these are generalized determinations, not physical laws.
This table is very helpful in determining the nature of a bond by finding the difference in electronegativity between two bonding atoms. However, it is not necessary to have the actual values. Knowing the relative electronegativity is usually enough for AP questions to generalize if a bond is ionic or covalent.
The atom in a chemical bond with a higher electronegativity will develop a partial negative charge, due to its pull on the electrons within the bond itself.
Please watch the following video on Bond Notation. Be sure you have your volume turned on!
You Try It!
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