Problem 26 - A Complete Resource Book in Chemistry for JEE Main

Question

The outermost electronic configuration of the most electronegative element is (a) \(\mathrm{ns}^{2} \mathrm{np}^{3}\) (b) \(\mathrm{ns}^{2} \mathrm{np}^{4}\) (c) \(\mathrm{ns}^{2} \mathrm{np}^{5}\) (d) \(\mathrm{ns}^{2} \mathrm{np}^{6}\)

Step-by-Step Solution

Answer

(c) \( \mathrm{ns}^{2} \mathrm{np}^{5} \).

Step 1: Identify the Most Electronegative Element

The most electronegative element in the periodic table is fluorine. This is important because electronegativity is the measure of an atom's ability to attract and hold onto electrons, and fluorine is known to have the highest value.

Step 2: Recall Fluorine's Position in the Periodic Table

Fluorine is located in the second period (row) of the periodic table and falls into group 17, also known as the halogens. This positioning helps in determining the electronic configuration.

Step 3: Determine the Electronic Configuration of Fluorine

For any element, the electronic configuration is dictated by its position. Fluorine, being in the second period with atomic number 9, has an electronic configuration which is: - 1s² 2s² 2p⁵ The outermost electron arrangement here is - 2s² 2p⁵.

Step 4: Match Configuration to Given Options

The outermost electron configuration of fluorine is - 2s² 2p⁵. This matches with the option (c) \( \mathrm{ns}^{2} \mathrm{np}^{5} \).

Step 5: Select the Correct Answer

Based on the information above, the correct answer that matches the outermost electronic configuration of the most electronegative element (fluorine) is:(c) \( \mathrm{ns}^{2} \mathrm{np}^{5} \).

Key Concepts

Electronegativity

Electronegativity is a chemical property that describes the ability of an atom to attract and hold onto electrons in a chemical bond. It varies across the periodic table and is an important factor in determining how atoms interact in molecules.

A general trend is that electronegativity increases as you move from left to right across a period, and decreases as you move down a group. This means that elements like oxygen and fluorine, located at the top right of the periodic table (excluding the noble gases), are among the most electronegative.

Fluorine, in particular, boasts the highest electronegativity value of all elements, with a value of approximately 3.98 on the Pauling scale.

• It's this high electronegativity that makes fluorine highly reactive, especially with metals, to form compounds like fluorides.
• The high value also dictates the way it shares electrons in bonds, often pulling them closer to itself compared to other elements.

Understanding the concept of electronegativity is crucial for predicting the types and strength of bonds that can form between different elements.

Periodic Table

The periodic table is a comprehensive chart that organizes all known elements according to their atomic number, electron configurations, and recurring chemical properties. It is structured in a way that reflects the periodicity or regular pattern of element properties.

There are several important aspects to note about the periodic table:

• Elements are arranged in increasing order of their atomic number, which is the number of protons in an atom's nucleus.
• Horizontal rows are called periods, and each period indicates the filling of a new electron shell or energy level.
• Vertical columns are groups or families of elements that share similar chemical and physical properties due to having the same outer electron configuration.

Period 2 of the table includes elements from lithium to neon, and these elements progressively fill the second electron shell. The group number for halogens such as fluorine is 17, signifying that these elements have seven valence electrons, just one short of achieving a full octet.

Knowledge of the periodic table is essential for understanding element behavior and predicting how they might interact with each other in chemical reactions.

Halogens

Halogens are a group of elements found in Group 17 of the periodic table. This group includes fluorine, chlorine, bromine, iodine, and astatine.

Some key characteristics of halogens include:

• They are non-metals and are very reactive, especially with alkali and alkaline earth metals.
• Due to having seven valence electrons in their outer shell, halogens are just one electron short of a complete octet, making them highly reactive as they seek to gain that additional electron through bonding.
• They form diatomic molecules, such as F₂ and Cl₂, in their elemental state due to their high reactivity; this is a stable configuration for them.

Fluorine is at the top of this group and is the most reactive. Its high electronegativity and reactivity make it a key substance in forming compounds.

Each halogen has distinct uses and characteristics, yet they share common chemical properties due to their similar valence electron configurations. Understanding these characteristics helps in predicting reactions and synthesizing new compounds using halogens.