Shaludheen S

Electronic configuration and stability

The arrangement of eight electrons in the outermost shell is called octet electron configuration. Octet electron configuration in an atom is a stable arrangement. Therefore, usually, these atoms do not take part in chemical reactions. 

The atoms without eight electrons in the outermost shell are unstable. Atoms acquire stability by attaining an eight electron configuration in their outer shell through chemical bonding.

Chemical bond

The attractive force that holds the atom together in a molecule is called a chemical bond. Mainly two types,

1. Ionic bond
2. Covalent bond

Ionic bond: The chemical bond formed by the transfer of electrons.

E.g., NaCl

The electronic configuration of Na is 2,8,1, whereas Cl is 2,8,7. To attain octet electron configuration, one electron from Na is transferred to Cl. Hence the configuration becomes 2,8 for Na and 2,8,8 for Cl.

Covalent bond: The chemical bond formed by the sharing of electrons. Mainly three types:

1. Single bond – formed by sharing one pair of electrons. e.g., CCl4, F2 
2. Double bond – formed by sharing two pairs of electrons. e.g., O2
3. Triple bond – formed by sharing three pairs of electrons. e.g., N2

Single bond: 

e.g., F2

When two fluorine atoms combine each other if one fluorine transfer one electron to another, the configuration of one fluorine becomes 2,6 and another become 2,8, the only one fluorine becomes stable. So there is no possibility of transferring electrons from one fluorine atom to another. Hence the two fluorine atoms attain octet electron configuration by sharing two electrons (one from the first F and another from the second F).

E.g., CCl4

The electronic configuration of carbon is 2,4, and chlorine is 2,8,7. Carbon and chlorine atoms require 4 and 1 electrons, respectively, to acquire octet electron configuration. One chlorine can share one electron, but carbon needs 4 electrons. Hence one carbon and four chlorine atoms combine to form CCl4.

Why is covalent compound important for carbon?

Carbon does not form ionic bonds because it has four valence electrons, half of an octet. To form ionic bonds, Carbon molecules must either gain or lose 4 electrons. It is highly unfavourable; therefore, carbon molecules share their four valence electrons through single, double, and triple bonds so that each atom can achieve octet electron configurations.