**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 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), 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 quite electronegative but not the highest. - **Oxygen (O)**: Located in Group 16, it has an electronegativity of about 3.44. Oxygen is 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 because it is the most electronegative element, effectively attracting electrons due to its small atomic size and high nuclear charge. 3. **Why Fluorine is the Highest**: - Fluorine's small atomic radius means that its valence electrons are close to the nucleus, allowing it to exert a strong pull on electrons from other atoms. - It has a high effective nuclear charge, which means that the protons in the nucleus can attract electrons more effectively than in larger atoms. ### Explanation of Why Other Options are Incorrect - **A. Sodium (Na)**: - Sodium is an alkali metal with a low electronegativity (0.93). It readily loses its single valence electron to form positive ions (Na⁺) rather than attracting electrons. Thus, it cannot be the most electronegative element. - **B. Chlorine (Cl)**: - While chlorine is quite electronegative (3.16), it is not as electronegative as fluorine. Chlorine can attract electrons effectively, but fluorine's ability to attract electrons is stronger due to its smaller size and higher nuclear charge. - **C. Oxygen (O)**: - Oxygen has a high electronegativity (3.44) and is very effective at attracting electrons. However, it is still lower than fluorine. Oxygen is often involved in forming polar covalent bonds, but it does not surpass fluorine in electronegativity. ### 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) due to its small size and high nuclear charge. - **Sodium (Na)** has low electronegativity (0.93) and tends to lose electrons. - **Chlorine (Cl)** and **Oxygen (O)** have higher electronegativities than sodium but are lower than fluorine. This understanding of electronegativity is crucial for predicting how different elements will interact in chemical reactions, especially in the formation of ionic and covalent bonds.