Problem 39 - A Complete Resource Book in Chemistry for JEE Main

Question

The electronic configuration of the most electronegative element is (a) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{5}\) (b) \(\mathrm{Is}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{4}, 3 \mathrm{~s}^{1}\) (c) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{6}, 3 \mathrm{~s}^{1}, 3 \mathrm{p}^{5}\) (d) \(1 \mathrm{~s}^{2}, 2 \mathrm{~s}^{2}, 2 \mathrm{p}^{6}, 3 \mathrm{~s}^{2}, 3 \mathrm{p}^{5}\)

Step-by-Step Solution

Answer

(a) \(1s^2, 2s^2, 2p^5\) is the electronic configuration of the most electronegative element, Fluorine.

Step 1: Identify the Most Electronegative Element

The most electronegative element in the periodic table is Fluorine. It's known for its high electronegativity due to its high atomic number within its period and small atomic radius.

Step 2: Recall the Electron Configuration of Fluorine

The electron configuration describes how electrons are distributed in an atom's orbitals. For Fluorine, with atomic number 9, the electronic configuration is: \[1s^2, 2s^2, 2p^5\]

Step 3: Compare Given Configurations with Fluorine's

Now match the options provided with the electronic configuration of Fluorine. Only the configuration in option (a), \(1s^2, 2s^2, 2p^5\), matches that of Fluorine.

Key Concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that describes an atom's tendency to attract and hold onto electrons. This property varies among elements and is essential for understanding how atoms interact in chemical bonds.
If an atom has high electronegativity, it strongly attracts electrons towards itself when forming chemical bonds. Conversely, atoms with low electronegativity attract electrons weakly.
Factors influencing electronegativity include:

• Atomic number: Generally, as the atomic number increases in a period, electronegativity increases because more protons in the nucleus exert a stronger pull on the electron cloud.
• Atomic radius: Within the same group, as the atomic radius increases, electronegativity typically decreases.

Understanding electronegativity helps predict how atoms will bond, identify polar and non-polar molecules, and determine reactivity. It is a key concept in explaining chemical reactions and molecular formation.

Fluorine

Fluorine holds the title as the most electronegative element in the periodic table. Its atomic number is 9, which means it has 9 protons and 9 electrons when neutrally charged.
The electron configuration for Fluorine is \[1s^2, 2s^2, 2p^5\]. This configuration hints at why Fluorine is so electronegative. It fills its 2p orbital with five electrons, leaving only one spot empty for a total of 8, the most stable arrangement known as the octet configuration.

Characteristics of Fluorine include:

• Small Atomic Radius: Fluorine's small size means the nucleus can exert a stronger force on its outer electrons, making it extremely effective at attracting additional electrons.
• High Reactivity: Due to its high electronegativity and desire to achieve a stable octet, Fluorine reacts vigorously with most other elements.

Fluorine’s high electronegativity and reactivity make it a critical component in many chemical reactions, particularly in organic chemistry and industrial applications.

Atomic Number

The atomic number is a crucial aspect of an element's identity, defining the number of protons found in the nucleus of an atom. It is denoted by the symbol \(Z\) and determines both the element's position in the periodic table and its chemical properties.

For example, Fluorine's atomic number is 9. This tells us:

• Fluorine has 9 protons in its nucleus.
• In a neutral atom, it also has 9 electrons arranged around the nucleus.

Knowing the atomic number allows scientists to predict how an atom will interact with others, as atoms with similar numbers of protons tend to exhibit similar behaviors.

The atomic number not only determines the identity of an element but also its location in the periodic table, influencing its grouping with elements of similar chemical reactivity. This classification helps make sense of the periodic table's organization and the trends seen across different periods and groups.