) Which Lewis structure below correctly represents KCl? A) K:Cl: B) K[:Cl:] C) K[Cl] D) :K:::Cl: E) none of the above 8) Which one of the following is the correct orbital diagram for nitrogen? A) B) C) D) E) none of the above
The Correct Answer and Explanation is:
Here are the correct answers and a detailed explanation for the questions provided in the image.
Correct Answers:
7. B
8. C
Explanation
7. Which Lewis structure below correctly represents KCl?
The correct answer is B. Potassium chloride (KCl) is an ionic compound. This type of compound forms between a metal (potassium) and a nonmetal (chlorine). In ionic bonding, electrons are not shared as they are in covalent bonds. Instead, they are completely transferred from the metal to the nonmetal.
- Potassium (K) is in Group 1 of the periodic table, so it has one valence electron. To achieve a stable electron configuration like a noble gas, it readily loses this single electron, forming a positively charged ion, or cation (K⁺).
- Chlorine (Cl) is in Group 17 (the halogens), so it has seven valence electrons. To achieve a stable octet (eight valence electrons), it readily accepts one electron, forming a negatively charged ion, or anion (Cl⁻).
The correct Lewis structure for an ionic compound must show this transfer. It represents the resulting ions with their respective charges. The cation (K⁺) is shown without any valence dots because it has lost its outer electron. The anion (Cl⁻) is shown with a full octet of eight valence electrons, enclosed in brackets with the negative charge written outside.
Option B, K⁺[:Cl:]⁻, is the only choice that accurately depicts the potassium cation and the chloride anion with its complete octet, representing the ionic bond in KCl correctly.
8. Which one of the following is the correct orbital diagram for nitrogen?
The correct answer is C. To determine the correct orbital diagram for nitrogen (N), we must follow three key principles of electron configuration:
- Aufbau Principle: Electrons fill the lowest energy orbitals first (1s, then 2s, then 2p, etc.).
- Pauli Exclusion Principle: An orbital can hold a maximum of two electrons, and they must have opposite spins (represented by an up arrow and a down arrow).
- Hund’s Rule: When filling orbitals of equal energy (degenerate orbitals), such as the three p orbitals, electrons are placed in separate orbitals with parallel spins before any are paired.
Nitrogen has an atomic number of 7, meaning a neutral atom has 7 electrons.
- The first two electrons fill the 1s orbital: 1s² (↑↓).
- The next two electrons fill the 2s orbital: 2s² (↑↓).
- The remaining three electrons go into the 2p orbitals. According to Hund’s rule, one electron is placed in each of the three 2p orbitals, and they all have the same (parallel) spin: 2p³ (↑) (↑) (↑).
Therefore, the complete orbital diagram is (↑↓) (↑↓) (↑) (↑) (↑). Option C correctly illustrates this arrangement
