Problem 63 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following has the highest electronegativity? (a) \(\mathrm{K}\) (b) B (c) \(\mathrm{Cl}\) (d) \(\mathrm{Na}\)

Step-by-Step Solution

Answer

Chlorine (9) has the highest electronegativity.

Step 1: Understand the Concept of Electronegativity

Electronegativity is the ability of an atom to attract electrons in a chemical bond. Generally, electronegativity increases across a period (from left to right) and decreases down a group in the periodic table.

Step 2: Locate the Elements on the Periodic Table

Identify the positions of the elements in the periodic table. - Potassium (0) is in Group 1 and Period 4. - Boron (B) is in Group 13 and Period 2. - Chlorine (9) is in Group 17 and Period 3. - Sodium (1) is in Group 1 and Period 3.

Step 3: Apply Electronegativity Trends

Using the periodic table trends, identify that Group 17 elements have high electronegativity values compared to Group 1. Electronegativity increases across a period and decreases down a group, indicating that chlorine (9), located in Group 17, will have higher electronegativity than the other listed elements.

Step 4: Conclusion Based on Trends

Based on periodic trends, chlorine (9) is likely to have the highest electronegativity out of the given options. This is because it is near the top right of the periodic table where the highest electronegative elements (excluding noble gases) are located.

Key Concepts

Understanding Periodic Trends

Periodic trends are patterns observed across different rows and columns of the periodic table. These trends help chemists predict the behavior and properties of elements. One such trend is electronegativity, which tends to increase across a period (left to right) and decrease down a group (top to bottom). This means that elements on the rightmost side of the periodic table, especially in the uppermost rows, often have higher electronegativity values. This is because they have more protons that can attract electrons from other atoms more effectively. As a result, understanding these trends is crucial in determining chemical properties like reactivity and bond formation. Chlorine, for instance, is highly electronegative due to its position near the top right of the periodic table.

Navigating the Periodic Table

The periodic table is a systematic arrangement of all known chemical elements. The table is organized into rows called periods and columns called groups or families. Each element's position in the periodic table reveals important information about its electron configuration and chemical behavior. For instance, elements in the same group usually exhibit similar chemical properties because they have the same number of valence electrons.
The periodic table is divided into blocks which roughly correspond to the subshell being filled with electrons:

• The s-block includes Groups 1 and 2.
• The p-block includes Groups 13 to 18.
• The d-block, also known as the transition metals, includes Groups 3 to 12.

Understanding the layout of the periodic table allows chemists to predict an element’s properties, such as electronegativity, based on its position. For example, chlorine is located in Group 17, known for high electronegativity values.

The Nature of Chemical Bonds

A chemical bond is a connection formed between atoms when they share or transfer electrons. Electronegativity plays a critical role in determining the type of bond formed.

• In an ionic bond, electrons are transferred from one atom to another, often between elements with significantly different electronegativities.
• Covalent bonds involve the sharing of electrons between atoms and typically occur between elements with similar electronegativities.
• Polar covalent bonds are a type of covalent bond where the electrons shared between atoms are not equally distributed because one atom is more electronegative than the other.

Electronegativity differences between atoms in a bond help predict the bond’s character. A greater difference in electronegativity suggests a more ionic character, while a smaller difference implies a covalent character. In our case, chlorine's high electronegativity means it tends to form polar covalent bonds, where it strongly attracts the shared electrons.