**Correct Option: C. Fluorine (F)** ### Explanation of the Correct Answer Electronegativity is a measure of an atom's ability to attract and hold onto electrons when it is part of a compound. The Pauling scale is one of the most commonly used scales to quantify electronegativity, and it assigns values to elements based on their ability to attract electrons in a chemical bond. 1. **Understanding Electronegativity**: - Electronegativity increases across a period (from left to right on the periodic table) because the number of protons in the nucleus increases, which enhances the positive charge and the ability to attract electrons. - Electronegativity decreases down a group (from top to bottom) because the additional electron shells increase the distance between the nucleus and the valence electrons, reducing the nucleus's pull on the bonding electrons. 2. **Position of Elements in the Periodic Table**: - **Sodium (Na)**: Located in Group 1 (alkali metals), sodium has a low electronegativity of about 0.93. Alkali metals tend to lose electrons easily rather than attract them. - **Chlorine (Cl)**: Found in Group 17 (halogens), chlorine has a higher electronegativity of about 3.16. It is quite effective at attracting electrons but is not the highest. - **Oxygen (O)**: Located in Group 16, oxygen has an electronegativity of about 3.44. It is very electronegative but still lower than fluorine. - **Fluorine (F)**: Positioned in Group 17, fluorine has the highest electronegativity value of 4.0 on the Pauling scale. This is due to its small atomic size and high effective nuclear charge, which allows it to attract electrons very strongly. 3. **Comparison of Electronegativity Values**: - Na: 0.93 - Cl: 3.16 - O: 3.44 - F: 4.0 From these values, it is clear that fluorine has the highest electronegativity. ### Explanation of Why Other Options Are Incorrect - **A. Sodium (Na)**: Sodium is an alkali metal with a very low electronegativity. It tends to lose its single valence electron rather than attract electrons, making it the least electronegative among the options provided. - **B. Chlorine (Cl)**: While chlorine is highly electronegative, it is not the highest. Its electronegativity of 3.16 is lower than that of fluorine. Chlorine is effective at attracting electrons, but fluorine's smaller size and higher nuclear charge give it a stronger ability to attract electrons. - **D. Oxygen (O)**: Oxygen is indeed very electronegative (3.44), but it still does not surpass fluorine. Oxygen's ability to attract electrons is strong, but fluorine's position in the periodic table gives it the edge. ### Common Pitfalls - **Confusing Electronegativity with Electron Affinity**: Electronegativity is about how well an atom attracts electrons in a bond, while electron affinity refers to the energy change when an electron is added to a neutral atom. They are related but distinct concepts. - **Overlooking Periodic Trends**: Students may forget that electronegativity increases across a period and decreases down a group, which is crucial for determining the correct answer. ### Revision Summary - **Fluorine (F)** has the highest electronegativity on the Pauling scale (4.0). - Electronegativity increases across a period and decreases down a group. - Sodium (Na) has the lowest electronegativity among the options. - Chlorine (Cl) and oxygen (O) are highly electronegative but less so than fluorine.