**Correct Option: D. 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. 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 outer electrons. 2. **Position of Elements in the Periodic Table**: - **Sodium (Na)**: Located in Group 1 (alkali metals), it has a low electronegativity of about 0.93. Alkali metals tend to lose electrons easily rather than attract them. - **Chlorine (Cl)**: Located in Group 17 (halogens), it has a higher electronegativity of about 3.16. Chlorine is very effective at attracting electrons, but it is not the highest. - **Oxygen (O)**: Located in Group 16, it has an electronegativity of about 3.44. Oxygen is also very electronegative, but still lower than fluorine. - **Fluorine (F)**: Located in Group 17, it has the highest electronegativity value of 3.98 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**: - **Fluorine (F)**: 3.98 - **Oxygen (O)**: 3.44 - **Chlorine (Cl)**: 3.16 - **Sodium (Na)**: 0.93 From this comparison, 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 quite electronegative, it is not as electronegative as fluorine. Chlorine's ability to attract electrons is strong, but it is outmatched by fluorine's stronger pull due to its smaller atomic radius and higher effective nuclear charge. - **C. Oxygen (O)**: Oxygen is indeed very electronegative, but it still does not reach the level of fluorine. The difference in electronegativity between oxygen and fluorine is significant enough to place fluorine at the top of the scale. ### Summary of Key Points - **Electronegativity** measures an atom's ability to attract electrons in a bond. - **Fluorine (F)** has the highest electronegativity on the Pauling scale (3.98). - **Oxygen (O)** and **Chlorine (Cl)** are also electronegative but lower than fluorine. - **Sodium (Na)** has the lowest electronegativity among the options, being an alkali metal. ### Revision Summary - Electronegativity increases across a period and decreases down a group. - Fluorine is the most electronegative element (3.98) on the Pauling scale. - Sodium has the lowest electronegativity (0.93) among the options. - Understanding the periodic trends is crucial for determining electronegativity values.