Covalent bond

Atoms of non-metals achieve duplet/ octet structure by sharing electrons with each other

Both non-metals have relatively large ionization energy and neither non-metal atom wants to lose its valence electron(s)

It is the electrostatic force of attraction between the shared pair(s) of electrons and the positive nuclei of the two bonding atoms.

they exist as diatomic molecules (except noble gases)

valence: 4 bonding pairs: 4 lone pairs: 0

valence: 5 bonding pairs: 3 lone pairs: 1

valence: 6 bonding pairs: 2 lone pairs: 2

valence: 7 bonding pairs: 1 lone pairs: 3

Hydrogen and Group VII/ 17 elements form single covalent bonds by each atom sharing one pair of electrons :

Group VI/ 16 elements form double bonds by sharing 2 pairs of electrons

Group V/ 15 elements form triple bonds by sharing 3 pairs of electrons

it is the distance between the nuclei of the two bonding atoms joined by covalent bond

it is the strength of electrostatic force between the shared pair of electrons and the nuclei of the two bonding atoms.

Bond strength can be measured in terms of bond energy (unit : kJ mol-1).

It is the energy required to break one mole of covalent bonds from gaseous molecules.

● As the atomic radius increases, the bond length increases. ● The shared pair of electrons in the covalent bond are further away from the nuclei of the two bonding atoms. ● Weaker electrostatic force of attraction → weaker covalent bond → lower bond energy.

● As the number of shared pair electrons in the covalent bond increases, the electrostatic force of attraction from the nuclei increases. ● The atoms are held closer and so the covalent bond is shorter and stronger. ● Bond strength: triple bond > double bond > single bond

● Some atoms, like Be(Beryllium) and B(Boron), form stable compounds with incomplete octets. ● They prefer to form covalent bond rather than ionic bond because of their comparatively high ionization energies.

To achieve octet structure in atoms like Be and B, they form dative covalent bond

it is a covalent bond which both electrons in the shared pair are contributed by the same atom

Dative covalent bond is also formed when species with lone pair electrons, such as ammonia and water, react with hydrogen ions (H+), it is also found in carbon monoxide

An arrow is usually used to represent the presence of a dative covalent bond.

Step 1 : Identify the total number of valence electrons. Step 2 : Identify both central atom and surrounding atoms of the species and arrange the “skeleton” of the species. Step 3 : Put the valence electrons to the “skeleton” of the species as bonding electrons in such a way that the surrounding atoms can form the expected number of covalent bonds. Step 4 : Put the remaining valence electrons to the surrounding atoms as their lone pair(s) of electrons in such a way that they can achieve octet structure of electrons. If some still remain, put to the central atom as its lone pair(s).

● Limited to the binary covalent compounds - formed between two different non-metals. • The first element written in the formula should be named first using its full name. • The second element in the formula should be named after the first one with the suffix of “ide”. • Prefix(es) should be included to indicate the number of each atom present in the molecule. • If the number of atom of the first element is one, then no prefix is needed.