Final answer:
Electronegativity defines how strongly atoms attract electrons in covalent bonds. Oxygen is the most electronegative, followed by nitrogen, carbon, and hydrogen. This difference in electronegativity is crucial for properties like basicity in nitrogen compounds and hydrogen bonding in biological molecules.
Step-by-step explanation:
The question pertains to the electronegativity of the essential life atoms: oxygen (O), nitrogen (N), carbon (C), and hydrogen (H). Electronegativity is the ability of an atom to attract electrons toward itself when forming a covalent bond. Higher electronegativity values indicate a stronger attraction for electrons. Among the elements O, N, C, and H, oxygen has the highest electronegativity with a value of 3.44, making it highly capable of attracting electrons in a chemical bond. Nitrogen follows with a value of 3.0, contributing to the formation of polar bonds in molecules such as amino bases which are basic because of nitrogen's tendency to donate its lone pair of electrons. Carbon has lesser electronegativity at 2.55, and hydrogen, the least of the four, with a value of 2.20.
This difference in electronegativity is particularly significant in the context of hydrogen bonds, where hydrogen is bonded to a stronger electronegative atom like oxygen or nitrogen. The resulting partial positive charge on hydrogen allows it to form hydrogen bonds with neighboring electronegative atoms, a key aspect in the structure and function of biological molecules. For example, the O-H bond in water is greatly polarized due to oxygen's higher electronegativity, resulting in an uneven electron distribution that is visualized as a high electron density (anion) around oxygen and a lower density (cation) around hydrogen.