Which of the following molecules cannot be formed by typical covalent bonds?

• A. H\(_2\)O
• B. He\(_2\)
• C. O\(_2\)
• D. N\(_2\)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand what typical covalent bonds are. Covalent bonds form when atoms share pairs of electrons to achieve a full outer shell, usually following the octet rule for main group elements.
2. Step 2: Analyze each molecule to see if it can form stable covalent bonds. For example, H\(_2\)O (water) forms covalent bonds between hydrogen and oxygen atoms, satisfying the octet rule for oxygen and duet for hydrogen.
3. Step 3: Consider O\(_2\) (oxygen molecule), which forms a double covalent bond between two oxygen atoms, sharing electrons to complete their octets.
4. Step 4: Look at N\(_2\) (nitrogen molecule), which forms a very strong triple covalent bond between two nitrogen atoms, sharing three pairs of electrons to satisfy the octet rule.
5. Step 5: Examine He\(_2\) (helium molecule). Helium is a noble gas with a full outer shell and does not typically form covalent bonds because it has no tendency to share electrons. Therefore, He\(_2\) cannot be formed by typical covalent bonds.