Following is a structural formula of the prescription drug famotidine, marketed by

Key concept

Lewis structure
A Lewis structure, also known as a Lewis dot diagram, is a representation of the valence electrons of an atom or molecule.

In a Lewis structure, the valence electrons of an atom are represented by dots placed around the symbol of the element. The number of dots is equal to the number of valence electrons in the atom.

Steps involved in drawing a lewis structure

1. Firstly, find the total number of valence electrons in the given molecule or ion. For this, add the number of valence electrons contributed by each atom.

2. Find out how the atoms are arranged in the given molecule or ion.

3. Connect the atoms with a single bond and then group the rest of the electrons in pairs so that each atom in the molecule or ion has a complete outer shell.

4. Each pair of bonding electrons shared between two atoms is shown as a single line between the atoms and a pair of dots represent an unshared pair of electrons.

5. A single bond is formed when there is a single pair of electrons between two atoms and a single line is drawn between them. A double bond (two lines) is formed when there are two pairs of electrons between two atoms. And a triple bond (three lines) is formed when there are three pairs of electrons between two atoms.

Formal charge is used to represent that electrons are distributed equally to each atom and it also shows that an atom has more or less electrons than the valence electrons of the same atom.

Step 1 of 3

We are given the structural formula of the drug famotidine, also known under the name Pepcid. The primary clinical use of Pepcid is for the treatment of active duodenal ulcers and benign gastric ulcers. Pepcid is a competitive inhibitor of histamine H2 receptors that reduces both gastric acid concentration and the volume of gastric secretions.

Famotidine

We have to complete the lewis structure of pepcid and describe each circled bond in terms of the overlap of atomic orbitals.