Problem 16 - A Complete Resource Book in Chemistry for JEE Main

Question

The outer most configuration of most electronegative element is (a) \(\mathrm{ns}^{2} \mathrm{np}^{5}\) (b) \(n s^{2} n p^{6}\) (c) \(\mathrm{ns}^{2} \mathrm{np}^{4}\) (d) \(\mathrm{ns}^{2} \mathrm{np}^{6}\)

Step-by-Step Solution

Answer

The outermost configuration of the most electronegative element is (a) \( \mathrm{ns}^2 \mathrm{np}^5 \).

Step 1: Understanding Electronegativity

Electronegativity is the ability of an atom to attract electrons in a chemical bond. Fluorine is the most electronegative element.

Step 2: Determine the Electron Configuration

Fluorine has an atomic number of 9. Its electron configuration is: 1s² 2s² 2p⁵. The outermost configuration (for the second shell) would thus be 2s² 2p⁵.

Step 3: Match the Configuration with Given Options

The outermost electron configuration of fluorine (2s² 2p⁵) corresponds to the general format ns² np⁵. Therefore, the correct answer is option (a) ns² np⁵.

Key Concepts

Electronegativity

Electronegativity is a fundamental property of atoms. It reflects how strongly an atom can attract and hold onto electrons in a bond. Think of it like atomic magnetism for electrons. This makes it a key player when predicting how atoms will interact in molecules.
Fluorine sits at the top of the electronegativity scale. Why? Because it has both a small atomic size and a high nuclear charge. This means the electrons in a bond are pulled strongly towards fluorine, giving it its reputation as a potent electron attractor. As a result, it plays a significant role in chemical reactions and bonding patterns. Understanding electronegativity can also help in predicting molecular shapes, bond strengths, and reactivity.

Fluorine

Fluorine is not just any element from the periodic table – it holds the title of the most electronegative element. This makes it a superstar in the chemistry world.
With an atomic number of 9, fluorine has the electron configuration of 1s² 2s² 2p⁵. This setup shows that fluorine is just one electron shy of having a full outer electron shell. The electron configuration tells us a lot about why fluorine is so reactive. Because it's eager to acquire that one extra electron to complete its shell, it participates actively in forming bonds.
The reactivity of fluorine makes it a crucial component in many compounds. On the industrial and commercial front, it’s essential in producing fluorinated hydrocarbons, used in refrigerants and other applications.

Electron Shells

Electron shells are like the layers of an onion, surrounding the nucleus of an atom. These shells contain the electrons and are organized by increasing energy levels. The first shell can hold 2 electrons, the second can hold 8, and so on, following the 2n² rule for maximum electrons in any shell n.
In fluorine, electrons fill up the first shell with 2 electrons and then the second shell with 7 electrons: 2s² 2p⁵. This electron distribution is what makes fluorine seek one more electron to fill its outer shell. A filled outer shell is also known as a stable, noble gas configuration, which is the ultimate goal for chemical stability.

• The closer an atom is to fulfilling this complete shell, the more it "wants" to gain or lose electrons during bonding.
• Electron shells also dictate an element's chemical properties and where it fits in the periodic table.

Periodic Table Trends

The periodic table is more than just a chart of elements; it's a map of elemental properties and trends. As you move across a period from left to right, electronegativity and ionization energy increase. This is due to the increasing positive charge of the nucleus, pulling electrons closer and more tightly.
Down a group, the trend is the opposite. Electronegativity decreases due to the added electron shells, which increase the distance between the nucleus and the outer electrons. This results in less pull on the bonding electrons.

• Fluorine, located at the top of group 17, exemplifies these trends, showcasing high electronegativity.
• The periodic trends help to predict and explain the chemical behavior of elements, explaining why fluorine's electronegativity is unmatched.

Knowing these trends allows chemists to predict how atoms will interact in chemical reactions, bond formation, and even in complex molecular structures.