Final answer:
The second-row elements such as carbon (C), nitrogen (N), oxygen (O), and fluorine (F) typically obey the octet rule by attaining eight electrons in their valence shell through chemical bonding to resemble the electron configuration of noble gases.
Step-by-step explanation:
Should the second-row elements obey the octet rule? The correct answer is Yes. The concept behind the octet rule is that atoms of main group elements, which include carbon (C), nitrogen (N), oxygen (O), and fluorine (F), combine in such a way that each atom has eight electrons in its valence shell, giving it the same electron configuration as a noble gas. For example, carbon, which has four valence electrons, satisfies the octet rule by forming four bonds, as in carbon tetrachloride (CCl4), while nitrogen, with five valence electrons, achieves an octet typically by forming three bonds and having one lone pair.
When predicting the number of bonds that an atom can form, we look at how many electrons are needed to reach an octet. This is particularly accurate for the nonmetals of the second period, which strictly follow this rule. However, there are exceptions to the rule, such as odd-electron molecules like nitric oxide (NO) that do not achieve an octet, and the heavier elements from the third period onwards, which can expand their valence shells due to available d orbitals.
In organic chemistry and molecular bonding theory, the octet rule is a foundational principle where elements combine to achieve a full valence shell resembling that of noble gases. Certain molecules and situations, such as those involving transition metals or expanded octet possibilities in higher-row elements, do not adhere strictly to the octet rule, but for second-row elements C, N, O, F, the rule is generally followed.