Question

Which one of the following represents the correct order of electronegativity? (a) \(\mathrm{P}>\mathrm{O}>\mathrm{N}\) (b) \(\mathrm{N}>\mathrm{P}>\mathrm{O}\) (c) \(\mathrm{O}>\mathrm{N}>\mathrm{P}\) (d) \(\mathrm{N}>\mathrm{O}>\mathrm{P}\)

Short answer

The correct order is (c) \( \mathrm{O} > \mathrm{N} > \mathrm{P} \).

Step-by-step solution

Understand Electronegativity

Electronegativity is a measure of how strongly an atom can attract electrons in a covalent bond. Atoms higher on the periodic table typically have higher electronegativity.

Compare Electronegativity Values

For the elements in the problem, Oxygen (O), Nitrogen (N), and Phosphorus (P): \( \text{Electronegativity of O} = 3.44 \), \( \text{N} = 3.04 \), and \( \text{P} = 2.19 \) according to the Pauling scale. Oxygen has the highest electronegativity, followed by Nitrogen, and Phosphorus has the lowest.

Determine the Correct Order

Based on the electronegativity values, the correct order from highest to lowest is Oxygen (O), Nitrogen (N), and Phosphorus (P).

Key concepts

Pauling scale

The Pauling scale is one of the most commonly used methods to quantify the electronegativity of an element. Developed by American chemist Linus Pauling, this scale assigns a value, without a unit, that typically ranges from about 0.7 to 4.0. The higher the value, the more an atom attracts electrons in a chemical bond.

Electronegativity is crucial in predicting how atoms will interact in a compound, especially in determining the type of bond that will form. For instance, when the difference in electronegativity between two atoms is significant, it indicates that the bond is likely to be polar, meaning electrons are not shared equally. An almost equal electronegativity value suggests a non-polar covalent bond.

For the elements in our exercise: Oxygen has an electronegativity of 3.44, Nitrogen has 3.04, and Phosphorus has 2.19. These values clearly show that oxygen is the most electronegative, emphasizing its tendency to attract electrons more strongly than nitrogen and phosphorus in a bond.

Periodic table trends

Electronegativity shows specific trends across the periodic table that can help predict an element's chemical behaviors. Understanding these trends makes it easier to anticipate how atoms will interact.

• Generally, electronegativity increases across a period from left to right. This is because atoms have more protons in their nuclei as you move across a period, increasing their positive charge and attraction for electrons.
• Electronegativity decreases down a group as you move from top to bottom. The added electron shells create a larger atomic radius, reducing the nucleus's pull on valence electrons.

With regards to the elements in our exercise, they are all in the same group but differ in periods: Oxygen and nitrogen are closer to the top of their respective periods and have higher electronegativities than phosphorus, which is further down.

Covalent bond

When atoms share electrons, they form a covalent bond. How strongly each atom attracts the shared electrons depends on their respective electronegativities. The more electronegative an atom, the more it pulls the electron density toward itself, creating a bond that can be polar if the electronegativity difference is significant.

In a polar covalent bond, the differences in electronegativity cause one end of the bond to be slightly negative while the other is slightly positive. In contrast, a non-polar covalent bond involves equal sharing of electrons, typical when both atoms have similar or identical electronegativities.

Using our examples from the exercise, when oxygen forms a bond with another atom, it typically holds the shared electrons closer to itself due to its high electronegativity. This feature often leads to polar covalent bonds, common in many biological and chemical processes.