Electronegativity

Electronegativity refers to the ability of an atom to attract electrons in a chemical bond. It generally increases across a period (left to right) and decreases down a group (top to bottom) in the periodic table.
- Sodium (Na) is an alkali metal with a low electronegativity.
- Chlorine (Cl) is a halogen, and it has high electronegativity but not the highest.
- Oxygen (O) has a high electronegativity but is still lower than that of fluorine.
- Fluorine (F) has the highest electronegativity of all elements, with a value of 3.98 on the Pauling scale.
Therefore, the element with the highest electronegativity is Fluorine.

Step 1: Understanding the Concept:
Electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself. Across a period in the periodic table, electronegativity increases as the nuclear charge increases and the atomic size decreases.

Step 2: Detailed Explanation:
All four elements belong to the second period of the periodic table: - D: Carbon (Group 14, ) - A: Nitrogen (Group 15, ) - B: Oxygen (Group 16, ) - C: Fluorine (Group 17, )
Across the period from left to right: C < N < O < F. [Image of periodic table trend for electronegativity]

Step 3: Final Answer
Following the periodic trend, the correct order is D < A < B < C.