Which of the following elements is most likely to form stable molecules in which the central atom has an incomplete octet?

• A. Boron (B)
• B. Nitrogen (N)
• C. Oxygen (O)
• D. Carbon (C)

Answer: (A)

Verified step by step guidance

1. Understand the concept of an incomplete octet: An incomplete octet occurs when the central atom in a molecule has fewer than 8 electrons in its valence shell after bonding. This is common for some elements, especially those in Period 2 of the periodic table.
2. Recall the typical valence electron counts and bonding behavior of the given elements: Boron (B) has 3 valence electrons, Nitrogen (N) has 5, Oxygen (O) has 6, and Carbon (C) has 4.
3. Recognize that Boron often forms compounds where it has only 6 electrons around it, such as in BF3, because it tends to form three covalent bonds and does not complete an octet.
4. Contrast this with Nitrogen, Oxygen, and Carbon, which typically form enough bonds to complete their octets (8 electrons) in stable molecules, following the octet rule more strictly.
5. Conclude that Boron is the element most likely to form stable molecules with an incomplete octet due to its electron deficiency and bonding patterns.