Problem 45 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Atomic radii of fluorine and neon in Ångstorm units are respectively given by (a) \(0.72,1.60\) (b) \(1.60,1.60\) (c) \(0.72,0.72\) (d) None of these values

Step-by-Step Solution

Answer

The correct answer is (a) 0.72 and 1.60 Å.

Step 1: Understanding Atomic Radii

The atomic radius is a measure of the size of an atom. It typically decreases across a period from left to right due to increasing positive charge in the nucleus, which draws electrons closer. Fluorine and neon are both in period 2 of the periodic table, but neon is a noble gas with a full outer shell.

Step 2: Evaluating Fluorine's Atomic Radius

Fluorine is a halogen with a relatively small atomic radius due to its high electronegativity and close electron configuration. The atomic radius of fluorine is around 0.64 Å to 0.72 Å.

Step 3: Evaluating Neon's Atomic Radius

Neon is a noble gas with a full electron shell, which generally have larger atomic radii due to filled energy levels leading to electron-electron repulsion in higher orbitals. The atomic radius for neon is usually around 1.60 Å.

Step 4: Matching Given Options to Known Values

Compare the known values to the given options. The option that matches is (a) with fluorine having a radius of 0.72 Å and neon having 1.60 Å.

Key Concepts

Periodic Table

The Periodic Table is an organized chart of elements arranged by increasing atomic number, which is the number of protons in the nucleus of an atom. Its layout helps to predict chemical behavior and properties of elements. For instance:

• Elements are organized in rows called periods and columns known as groups.
• Atomic radii generally decrease from left to right across a period due to increasing nuclear charge.
• As you move down a group, atomic radii increase because of added electron shells.

Atomic structure and reactivity can be inferred by an element's position in the table. Understanding the Periodic Table helps us understand why elements behave the way they do, like the small atomic radius of fluorine compared to the relatively large atomic radius of neon.

Atomic Structure

Atoms consist of a nucleus surrounded by electrons. This nucleus contains protons and neutrons. The atomic radius is largely determined by the electrons and how far they are from the nucleus.

• Protons have a positive charge, influencing electron attraction.
• Electrons are negatively charged and orbit the nucleus in energy levels or shells.
• Neon's larger atomic radius compared to fluorine is due to its full outer shell.

The balance between electron-electron repulsion in these outer shells and the attraction to the nucleus defines the size of the atom. This is why elements like noble gases with filled outer shells tend to have larger atomic radii.

Noble Gases

Noble gases, including neon, are a group of elements found in Group 18 of the Periodic Table. These gases are known for their stability and low reactivity.

• They have a full valence electron shell, like neon with eight electrons in its outer shell.
• Due to this full shell configuration, they have little tendency to gain or lose electrons.
• Their large atomic radius compared to other period elements is due to complete energy levels and electron cloud expansion.

Understanding noble gases illuminates why elements like neon maintain larger atomic radii, as the complete electron configuration repels additional electrons, increasing size. This explanation clarifies neon's atomic radius compared to other elements like fluorine.