A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.[1] For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.
Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, and three-center two-electron bonds.[2][3] The term covalent bond dates from 1939.[4] The prefix co- means jointly, associated in action, partnered to a lesser degree, etc.; thus a "co-valent bond", in essence, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H
2, the hydrogen atoms share the two electrons via covalent bonding.[5] Covalency is greatest between atoms of similar electronegativities. Thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons over more than two atoms is said to be delocalized
A simple view of covalent bonding
The importance of noble gas structures
At a simple level (like GCSE) a lot of importance is attached to the electronic structures of noble gases like neon or argon which have eight electrons in their outer energy levels (or two in the case of helium). These noble gas structures are thought of as being in some way a "desirable" thing for an atom to have.
You may well have been left with the strong impression that when other atoms react, they try to achieve noble gas structures.
As well as achieving noble gas structures by
transferring
electrons from one atom to another as in ionic bonding, it is also possible for atoms to reach these stable structures by sharing electrons to give covalent bonds.
 

Comments

Post a Comment

Popular posts from this blog

A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electrostatic force of attraction between opposite charges, either between electrons and nuclei , or as the result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole–dipole interactions , the London dispersion force and hydrogen bonding .
Read more
Image
Boron trifluoride, BF 3 A boron atom only has 3 electrons in its outer level, and there is no possibility of it reaching a noble gas structure by simple sharing of electrons. Is this a problem? No. The boron has formed the maximum number of bonds that it can in the circumstances, and this is a perfectly valid structure. Energy is released whenever a covalent bond is formed. Because energy is being lost from the system, it becomes more stable after every covalent bond is made. It follows, therefore, that an atom will tend to make as many covalent bonds as possible. In the case of boron in BF 3 , three bonds is the maximum possible because boron only has 3 electrons to share
Read more
Metallic bonding constitutes the electrostatic attractive forces between the delocalized electrons , called conduction electrons , gathered in an electron cloud and the positively charged metal ions. Understood as the sharing of "free" electrons among a lattice of positively charged ions ( cations ), metallic bonding is sometimes compared with that of molten salts ; however, this simplistic view [ which? ] holds true for very few [ which? ] metals . In a more quantum-mechanical view, the conduction electrons divide their density equally over all atoms that function as neutral (non-charged) entities. [ citation needed ] Metallic bonding accounts for many physical properties of metals, such as strength , ductility , thermal and electrical conductivity , opacity , and luster . [ 1 ] [ 2 ] [ 3 ] [ 4 ] Although the term "metallic bond" is often used in contrast to the term " covalent bond ", it is preferable [ by whom? ] to use the term metallic bon...
Read more