Pairs of outermost shell electrons which are not used in bonding are

Step 1: Analyze the question We need the term for pairs of electrons in the outermost shell that are not involved in bonding.

Step 2: Explain the concept In covalent bonding, outer-shell electrons fall into two groups:

• Bonding pairs (shared pairs): electrons shared between two atoms to form a covalent bond.
• Lone pairs (non-bonding pairs): pairs of outer-shell electrons that stay on one atom and are not shared.

Step 3: Examine the options

• A. Lone pairs: Correct. These are pairs of valence electrons not used in bonding.
• B. Bonding pairs: These are used in bonding, so this is the opposite of what the question asks.
• C. Valence electrons: This refers to all the electrons in the outermost shell, whether bonding or not. It is not specific to unshared pairs.
• D. Electrovalent electrons: This is not a standard term. "Electrovalent" refers to ionic bonding, which involves electron transfer.

Step 4: Example In ammonia (NH₃), nitrogen has 5 valence electrons. Three are used to form three N–H bonds, leaving one lone pair on nitrogen. In water (H₂O), oxygen has two lone pairs. These lone pairs affect molecular shape, which is why NH₃ is pyramidal and H₂O is bent.

Answer: A. lone pairs

Exam tip: Remember "lone = alone." A lone pair sits alone on one atom, while a bonding pair is shared between two atoms.