Problem 50 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

On Mulliken scale, the average of ionization potential and electron affinity is known as ..............

Step-by-Step Solution

Answer

On the Mulliken scale, it's called electronegativity.

Step 1: Understanding the Mulliken Scale

The Mulliken scale is a method of calculating electronegativity, which is a measure of an atom’s ability to attract and hold onto electrons.

Step 2: Definitions: Ionization Potential and Electron Affinity

Ionization potential (IP) is the energy required to remove an electron from an atom. Electron affinity (EA) is the energy change when an atom gains an electron. Both values are measured in electron volts (eV) or another energy unit.

Step 3: Calculating Average Values

To find the average of two numbers, add them together and divide by two. Similarly, the Mulliken scale calculates the average of the ionization potential and electron affinity to find a specific property of the atom.

Step 4: Applying the Mulliken Formula

According to the Mulliken scale, electronegativity (χ) of an atom can be calculated as the average of its ionization potential (IP) and electron affinity (EA): \[\chi = \frac{IP + EA}{2}\]

Key Concepts

Electronegativity

Electronegativity is a critical concept in chemistry that describes how strongly an atom can attract and hold electrons within a molecule. When atoms form bonds, electronegative atoms tend to pull the shared electrons closer to themselves, thereby affecting the distribution of electron density in a molecule. This can influence the molecule's reactivity, polarity, and overall stability. On the Mulliken scale, electronegativity is quantified by averaging two energetic properties of an atom: its ionization potential and electron affinity. This makes the Mulliken scale a unique way of assessing how an atom might behave in a chemical bond. Some important points about electronegativity are:

• Electronegativity values are dimensionless, and they provide a scalar quantity for comparing elements.
• Elements with high electronegativities, such as fluorine, oxygen, and nitrogen, are more polarizing because they attract electrons strongly.
• Electronegativity can influence various chemical phenomena, including dipole moment formation and hydrogen bonding.

Understanding electronegativity helps in predicting bond types and the behavior of elements in chemical reactions.

Ionization Potential

Ionization potential (IP) is the amount of energy needed to remove the outermost electron from an atom in the gaseous state, essentially transforming it into a cation. In simple terms, it reflects how firmly an atom's electrons are held. Higher ionization potentials mean that more energy is required to remove an electron, indicating that the electron is tightly bound. Here are some key aspects:

• The first ionization potential refers to the removal of the first electron, and it subsequently increases with each additional electron removed.
• Ionization potential is typically expressed in units of electron volts (eV).
• Elements with filled valence shells, like the noble gases, often have high ionization potentials because they are stable and less likely to lose electrons.

Ionization potential is crucial in determining an element’s chemical reactivity. Elements with lower ionization potentials tend to be more reactive as they can lose electrons more easily during chemical reactions.

Electron Affinity

Electron affinity (EA) measures the amount of energy released when an atom in the gaseous state gains an electron, converting it into an anion. This concept is critical because it helps to understand how easily an atom can accept additional electrons during chemical bonding. Consider these points:

• Electron affinity is typically a negative value, as energy is usually released when an electron is added to an atom.
• A high electron affinity value means that the atom releases more energy when it gains an electron, indicating a strong tendency to become negatively charged.
• Halogens, like chlorine, usually have high electron affinity values because they are very effective at gaining electrons to complete their valence shells.

Understanding electron affinity is essential in predicting how atoms will interact with one another in molecules, influencing both structure and reactivity of compounds.