Question

state why water has two lone pairs of electrons in its covalent molecule while Ammonia has one lone pair

Answer 1

In valance shell of centre atom of water i.e., oxygen , there are 6 electron . Out of these 6electron ,,2electron take part in forming bond with 2 Hydrogen atom , hence 4 electron , i.e., 2 lone pair are present.
whereas in ammonia ,centre atom is nitrogen which have 5electron in its valance shell, out of which 3electron form bond with 3 hydrogen atom this only 2 electron (1 lone pair) is present.

Answer 2

Complete its octet, oxygen has 6 valence electrons and therefore requires 2 additional electrons from 2 hydrogen atoms.

Explanation:

• Ammonia also has four electron pairs and the coordination geometry of nitrogen is based on the tetrahedral arrangement of the electron pairs.
• There are only three bonded groups, so there is a lone pair.
• A water molecule has two bond pairs and two lone pairs.
• For methane and ammonia, the domain geometry for a molecule with four electron pairs is tetrahedral.
• In a water molecule, the two electron pairs are lone pairs rather than bond pairs.
• In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bond and is sometimes called a shared pair or non-bonding pair.
• Lone pairs are found in the outermost electron shell of atoms.