Problem 93 - A Complete Resource Book in Chemistry for JEE Main

Question

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

Step-by-Step Solution

Answer

Option (c) is correct: fluorine 0.72 Å, neon 1.60 Å.

Step 1: Understanding Atomic Radius

The atomic radius is the size of an atom from its nucleus to the outer boundary of the surrounding cloud of electrons.

Step 2: Analyzing the Atomic Radius of Fluorine

Fluorine is a halogen and typically has a small atomic radius due to the effective nuclear charge pulling electrons close to the nucleus. Its usual atomic radius is around 0.72 Å.

Step 3: Analyzing the Atomic Radius of Neon

Neon is a noble gas with a filled outer electron shell, which typically results in a larger atomic radius compared to halogens like fluorine. Neon generally has an atomic radius of around 1.60 Å.

Step 4: Comparing Given Options

Compare the provided atomic radii: Option (a) gives both as 1.60 Å, option (b) gives both as 0.72 Å, option (c) gives fluorine as 0.72 Å and neon as 1.60 Å. Based on our analysis, option (c) is consistent with known atomic radii.

Key Concepts

Atomic Structure

Atomic structure refers to how atoms are organized. Each atom consists of a nucleus and an electron cloud. The nucleus, found at the center, contains protons and neutrons, while electrons move around the nucleus at various energy levels or shells. - **Nucleus**: This is positively charged due to protons. Neutrons do not have a charge but add to the mass. - **Electrons**: Negatively charged particles that orbit the nucleus. They determine the atom's chemical properties. The balance between protons and electrons makes atoms electrically neutral. Atomic structure defines how different atoms will interact with one another.

Atomic Size Comparison

When comparing atomic sizes, it's crucial to understand that atomic radius plays a role. Atomic radius is a measure from the nucleus to the outermost electron shell. - **Atomic Size Influencers**: The number of electron shells and the effective nuclear charge (the pull from the nucleus on the electrons) affect the atom's size. * Fluorine vs. Neon: Fluorine, a halogen, holds electrons closer due to higher nuclear attraction. Hence, it has a smaller atomic radius (about 0.72 Å). Neon, a noble gas, has a filled electron shell, making its atomic radius larger (about 1.60 Å). This comparison explains why some elements in the same period have differing atomic sizes.

Periodic Table Trends

The periodic table is a powerful tool for predicting elements' properties. Such trends often explain atomic size variations across periods and groups. - **Across a Period (Left to Right)**: Atomic radii generally decrease across a period. This is due to increased nuclear charge pulling electrons closer despite adding more electrons. - **Down a Group**: Atomic radii increase as each successive element adds a new electron shell, making the atom larger. For example, moving from fluorine to neon in the same period, we observe an increasing atomic radius. Although they are neighbors, neon has a larger atomic radius due to the enhanced shielding effect of its full electron shell.