Problem 151 - A Complete Resource Book in Chemistry for JEE Main

Question

How many electrons are present in Si atom corresponding to \(l=1\) ?

Step-by-Step Solution

Answer

8 electrons are present in Si atom corresponding to \(l=1\).

Step 1: Understand the Atomic Structure of Silicon

Silicon (Si) has an atomic number of 14, which means it has 14 electrons in a neutral atom. These electrons are arranged in different energy levels or shells around the nucleus.

Step 2: Recall the Quantum Numbers for Electrons

Electrons in an atom are defined by a set of quantum numbers: - The principal quantum number, \(n\), determines the shell level. - The azimuthal quantum number, \(l\), defines the subshell or orbital type (0 for s, 1 for p, 2 for d, and 3 for f). For \(l=1\), we are focusing on p orbitals.

Step 3: Electron Configuration of Silicon

The electron configuration of Si is: \[1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^2\] This shows where each electron of silicon is positioned according to its energy level and type.

Step 4: Identify Electrons in the \(l=1\) Orbitals

The configuration showing \(l=1\) (p orbitals) is - \(2p^6\) and - \(3p^2\). This means there are electrons in both the 2p and 3p subshells.

Step 5: Count the Electrons in \(l=1\) Orbitals

Add the electrons in the \(2p\) and \(3p\) orbitals: - \(6\) electrons in \(2p\) - \(2\) electrons in \(3p\) This equals a total of \(6 + 2 = 8\) electrons.

Key Concepts

Quantum Numbers

In atomic physics, quantum numbers are vital in describing every electron in an atom. Quantum numbers are like an address for electrons, locating their specific position and energy in an atom. They come as a set of four and tell us vital information:

• The principal quantum number ( ), which indicates the energy level or shell where the electron resides.
• The azimuthal quantum number ( l), which reveals the shape of the electron's orbital, such as s, p, d, or f orbitals.
• The magnetic quantum number (m_l), which specifies the orientation of the orbital in space.
• The spin quantum number (m_s), which describes the direction of the electron's spin, which can be either +1/2 or -1/2.

For the exercise, understanding , is crucial because it focuses on subshell and orbital types. In the exercise, l = 1 denotes a p orbital. Knowing quantum numbers helps determine the electron configuration and placement in atomic structures.

Atomic Structure

The atomic structure of an element reveals how its electrons are organized. Every element has a unique atomic number, which equals the number of protons and electrons in a neutral atom. The arrangement of electrons is vital to understanding an element's chemical properties and behavior.

Electrons inhabit energy levels or shells surrounding the nucleus. These shells are divided into subshells (like s, p, d, f), which house the electrons. Silicon, with an atomic number of 14, has 14 electrons. These electrons fill the shells in increasing energy order. For Si, the configuration is:

• 1s: 2 electrons
• 2s: 2 electrons
• 2p: 6 electrons
• 3s: 2 electrons
• 3p: 2 electrons

This specific arrangement highlights how electrons fill available spaces based on energy levels, allowing us to predict chemical properties and reactions.

P Orbitals

P orbitals are important in understanding electron arrangements in atoms. They occur at the azimuthal quantum number = 1 and are shaped like dumbbells, offering three possible orientations (along x, y, and z axes). This shape and orientation allow them to participate actively in bonding and molecular interactions.

In the silicon atom, p orbitals appear in the second and third energy levels, as indicated by its electron configuration: - 2p: 6 electrons - 3p: 2 electrons This shows that silicon utilizes its p orbitals in these two layers.

Understanding p orbitals is crucial because they contribute significantly to the atom's chemical properties. They can hold up to six electrons per energy level, filling in according to specific rules and affecting how atoms bond and form compounds. So, knowing how p orbitals work helps to comprehend the broader topic of chemical bonding and interactions.