In a covalent bond, a pair of electrons is shared between two atoms. Each of the positively charged nuclei is attracted to the same negatively charged pair of electrons.
A and B are held together by this shared attraction. Covalent bonds are often drawn as dots and crosses diagrams to show that the electrons have come from two different atoms. Molecules have a certain fixed number of atoms in them joined together by covalent bonds. Examples:
Bonding in hydrogen
Both hydrogen nuclei are strongly attracted to the shared pair of electrons The bond can be shown as: H-H: The line represents a pair of shared electrons. A hydrogen molecule consists of a pair of hydrogen atoms. They are diatomic because they contain 2 atoms.
When bonds are formed, energy is released. The more bonds an atom forms, the more energy is released and the more stable the system becomes.
Covalent bonding in hydrogen chloride molecule, HCl
Cl atom has 1 unpaired electron. It shares it with the H atom.
NB: Only the electrons in the outer energy level are used in boding. You can also leave out the inner electrons and the lone pairs (non-bonding pairs of electrons in the outer level)
The Significance of the noble gas structure in covalent bonding: Atoms that bond covalently produce outer electronic structures that are similar to those of the noble gases, i.e., 8 electrons in the outer shell (2.8.8. as in argon and same as helium 2.)
Bonding in chlorine
Bonding in methane
Bonding in oxygen
Bonding in ammonia, NH3
Bonding in carbon dioxide, CO2
Carbon has 4 unpaired electrons and so can form 4 covalent bonds. Each oxygen atom has two unpaired electrons and can form 2 covalent bonds.
Covalent Bonding in water, H2O
Ionic bonding is bonding in which there has been a transfer of electrons from one atom to another to produce ions. The substance is held together by...