Chemical Combination

Chemical Combination

Chemical combination is the reaction of two or more elements together to give products which can either be compounds or molecules. It is the combination of elements in the right proportion. The rare gases are very stable due to their electronic configuration. The tendency of other elements is to try to attain the stable duet or octet structure possessed by the rare gases. This is achieved during chemical combination. There are two types of chemical combinations:

• Electrovalent or ionic combination
• Covalent combination

Electrovalent Combination:

This is the total transfer of electrons from one atom (usually metallic) to another (usually non-metallic). We have atoms which act as donors of electrons and those which act as acceptors of electrons. It is only the outermost electron that is involved in chemical combination. The group one, two, and three elements whose valency is one, two, and three, respectively, require less energy to give away these electrons to attain stable duet or octet structure. The group of elements such as carbon does not transfer its electrons to all. The non-metal group 5, 6, and 7 need to accept 3, 2, and 1 electrons respectively to attain a stable octet configuration. After the metallic particles (elements) donate their electrons, they become positively charged; the non-metallic particles become negatively charged after acquiring extra electrons. These charged particles are known as ions.

Characteristics of Electrovalent Compounds

• Electrovalent compounds have high melting and boiling points because of the strong electrovalent ions.
• Ionic compounds readily dissolve in water.
• Ionic compounds can conduct electricity when melted or dissolved in water.
• Electrovalent compounds exist mainly as solids at room temperature.

Covalent Combination

Covalent combination is the sharing of a pair of electrons between two reacting atoms so that both can attain the stable octet structure. This pair of electrons is known as the "sharing pair". Each reacting atom contributes one member of the shared pair. Diatomic molecules of elements are formed by covalent combination, e.g., Chlorine (Cl₂) and hydrogen (H₂). The shared pair is represented by a stroke between them, called a single bond.

There are two types of covalent combinations: Ordinary covalent combination and coordinate covalent combination.

In ordinary covalent combination, the shared pair of electrons is contributed equally by the participating atoms, while in coordinate covalent combination, the shared pair of electrons is donated by only one of the participants.