Problem 28 - A Complete Resource Book in Chemistry for JEE Main

Question

The electronic configuration of four different elements is given below. Identify the group IV element among these. (a) \([\mathrm{He}] 2 \mathrm{~s}^{1}\) (b) \([\mathrm{Ne}] 3 \mathrm{~s}^{2}\) (c) \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{2}\) (d) \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{5}\)

Step-by-Step Solution

Answer

The Group IV element is Silicon (Si), represented by configuration (c).

Step 1: Understand Electron Configuration

In electron configuration, the numbers and letters represent the energy levels and types of orbitals that the electrons occupy. For example, in the configuration \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{2}\), \([\mathrm{Ne}]\) represents the filled configuration of neon, \(3s^2\) indicates two electrons in the 3s orbital, and \(3p^2\) indicates two electrons in the 3p orbital.

Step 2: Determine Total Number of Electrons

Calculate the total number of electrons each configuration represents by adding the electrons in all the depicted orbitals and the atomic number of any noble gas core. For example: \([\mathrm{He}] 2s^1\) has 2 electrons from He plus 1 electron from \(2s^1\), totaling 3 electrons.

Step 3: Identify the Elements

Identify the elements based on their total number of electrons (atomic number). - (a) has 3 electrons, corresponding to Lithium (Li) in Group I. - (b) has 12 electrons, corresponding to Magnesium (Mg) in Group II. - (c) has 14 electrons, corresponding to Silicon (Si) in Group IV. - (d) has 17 electrons, corresponding to Chlorine (Cl) in Group VII.

Step 4: Identify the Group IV Element

Group IV elements have four electrons in their outermost shell. Check for configurations with 4 valence electrons. The configuration \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{2}\) (c) totals to 4 valence electrons (2 in 3s and 2 in 3p), thus identifying it as a Group IV element.

Key Concepts

Electron Configuration

Electron configuration is a shorthand way of displaying how electrons fill up various orbitals within an atom. Each element on the periodic table has a unique configuration. This unique setup helps identify how and where electrons are distributed across various atomic shells and subshells. The configuration starts from the innermost shell and proceeds outward as energy levels fill. For example, writing \(\text{O: } 1s^2 2s^2 2p^4\), we learn that the element oxygen has 2 electrons in its 1s orbital, 2 in its 2s orbital, and 4 in its 2p orbital. Each section provides critical information regarding the electron's location and the general shape of their probability regions.

Group IV Elements

Group IV elements belong to the fourth column in the periodic table, and typically contain four valence electrons. This group includes carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). These elements share certain basic properties due to having the same number of valence electrons.
Group IV can be further divided into metals, non-metals, and metalloids:

• Carbon: A non-metal known for its allotropy which includes graphite and diamond.
• Silicon and Germanium: Metalloids with semiconductor properties highly valuable in electronics and computing.
• Tin and Lead: Metals often used in making alloys and weights respectively.

Understanding the shared characteristics and uses of Group IV elements reinforces the connection between an element's electron configuration and its position on the periodic table.

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom. These electrons play a pivotal role in chemical bonding and reactions as they are the most easily accessible to interact with other atoms. For example, carbon in Group IV has four valence electrons, represented as \(2s^2 2p^2\), indicating two electrons in the 2s orbital and two more in the 2p orbital. This configuration allows carbon to form four covalent bonds, an essential factor in the formation of organic molecules.

• They determine an element's reactivity.
• They are primarily responsible for the properties of an element.

Knowing how to identify valence electrons is essential for predicting behavior during chemical reactions.

Periodic Table Groups

The periodic table is organized into groups (vertical columns) and periods (horizontal rows), where groups hold elements with similar chemical properties. There are 18 groups in total, each offering insights into commonalities among elements based on their numbers of valence electrons. For instance, Group I contains elements like hydrogen and alkali metals, all having one valence electron.
Some key features of periodic groups include:

• Elements in the same group have identical outer electron configurations.
• These similar configurations lead to comparable chemical reactions and bonding behaviors.
• The periodic trend can help predict properties and potential uses based on electronic configuration.

Studying periodic table groups enhances our understanding of elemental behavior and their interactions.