Classification of Elements

After completion of this lesson, student must be able to:

  • Define valency as the combining capacity of elements.
  • Write molecular formula of some simple compounds.
  • Describe the types of chemical bonds in short.


Elements, Atoms and Compounds

An element is the simplest form of a pure substance, which cannot be split up into two or more simpler substances by any chemical reaction. A compound is a substance of atoms of two or more elements formed by the chemical combination in a definite proportion by weight. This note provides information about elements, compound, molecules, and atoms.

Radicals and Inert Gases

A radical is an atom or a group of atoms of different elements having positive or negative charge and acts as a single unit throughout the chemical reactions. This note provides information about radical, inert gases and

Electronic Configuration

The systematic distribution of an electron in different shells of an atom is called electronic configuration. The outermost orbit or shell of an atom is called valence shell and the number of electrons present in the valence shell of an atom is called valence electrons. This note provides information about electronic configuration, valence shell and valence electrons, valency and variable valency.

Chemical Bonding and Molecular Formula

Chemical Bonding

Chemical bonding is the force of attraction that binds atoms or group of atoms to form a stable chemical molecule or compound. For example, hydrochloric acid (HCL) is formed of one molecule of hydrogen and one molecule of chlorine.

Electrovalent bond

The chemical bond formed by the transfer of electrons from valence shell of an atom to the valence shell of another atom is called electrovalent bond and the valency is known as electrovalency.

Electrovalent bond is formed in between two atoms in which one atom belongs to metal and another is non-metal.

Covalent bond

The covalent bond is formed by the sharing of a pair of electrons between two atoms each contributing an equal number of electrons to the electron pair

Molecular Formula

  • Molecular formula of an element
  • Molecular formula of a compound