Problem 55 - A Complete Resource Book in Chemistry for JEE Main

Question

The electronic configurations of some elements are given below. The element with highest electron affinity is (a) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{3}\) (b) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{4}\) (c) \(1 \mathrm{ls}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{5}\) (d) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{2}\)

Step-by-Step Solution

Answer

(c) \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{5}\) for Fluorine has the highest electron affinity.

Step 1: Identify the Elements

We identify the elements associated with each of the electronic configurations provided: - (a): \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{3}\) corresponds to Nitrogen (N). - (b): \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{4}\) corresponds to Oxygen (O). - (c): \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{5}\) corresponds to Fluorine (F). - (d): \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{2}\) corresponds to Carbon (C).

Step 2: Understand Electron Affinity

Electron affinity is a measure of the energy released when an atom in the gaseous state accepts an electron. Generally, the higher the electron affinity, the more energy is released. This trend increases across a period from left to right.

Step 3: Compare Electron Affinities

Based on periodic trends, Fluorine (F) typically has the highest electron affinity among the elements given because it is in period 2, group 17, and thus desires an electron to complete its outer shell.

Step 4: Identify Element with Highest Electron Affinity

From the comparison, option (c) corresponding to Fluorine with the configuration \(1\mathrm{~s}^{2}, 2\mathrm{~s}^{2}, 2\mathrm{p}^{5}\) is the element with the highest electron affinity.

Key Concepts

Electronic Configuration

Electronic configuration refers to the distribution of electrons among the orbitals of an atom. It provides a detailed arrangement of electrons in the atomic orbitals and is crucial for understanding chemical properties. Each electron in an atom occupies a specific energy level and orbital.

• Each element has a unique electronic configuration, which can be expressed using the notation based on principal (\(n\)) and azimuthal quantum numbers.
• This notation also involves letter designations such as _s_, _p_, _d_, and _f_, representing different types of orbitals.
• For example, Oxygen has the electronic configuration: \(1 ext{s}^{2}, 2 ext{s}^{2}, 2 ext{p}^{4}\), indicating it has two electrons in the first energy level _s_-orbital, and in the second energy level it has two electrons in the _s_-orbital and four in the _p_-orbital.

Understanding electronic configurations helps in predicting chemical behavior, such as reactivity and bonding. For instance, elements with nearly filled _p_-orbitals, like Fluorine, are highly electronegative, seeking to fill their valence shell.

Periodic Trends

Periodic trends are patterns observed in the properties of elements as you move across a period or down a group in the periodic table. These trends provide invaluable insights into element behavior and chemical reactivity.

• _Atomic Size_: As you move across a period (from left to right), atomic size decreases due to increasing nuclear charge, pulling electrons closer to the nucleus.
• _Ionization Energy_: The energy required to remove an electron increases across a period. This means elements on the right side of the table, such as Fluorine, require more energy to remove an electron.
• _Electron Affinity_: Measures the energy release when an atom gains an electron. This trend generally increases across a period, implying that elements like Fluorine release more energy upon gaining an electron compared to elements on the left side of the period, such as Carbon.

Understanding periodic trends allows chemists to predict how an element might react based on its position in the periodic table. For instance, elements on the right side of a period tend to have higher electron affinities and lower atomic radii.

Gaseous State

The gaseous state is one of the fundamental states of matter, where the matter doesn't have a fixed shape or volume. Instead, it takes the shape of its container. Atoms or molecules in a gaseous state are spread far apart compared to solids and liquids.

• In this state, atoms or molecules have high kinetic energy, which allows them to move freely and collide with each other. This explains why gases expand to occupy the volume of their container.
• The gaseous state is significant in understanding atomic properties and reactivities, especially when discussing electron affinity. During a chemical reaction in the gaseous state, atoms can easily gain or lose electrons, highlighting their affinities.
• For example, when discussing electron affinities, values are usually considered under the gaseous state because this state reflects an atom's inherent tendency to attract electrons without external influences from surrounding materials.

Comprehending the gaseous state is essential in many chemical applications, including predicting and explaining reaction outcomes in atomic absorption and emission processes.