Problem 86 - A Complete Resource Book in Chemistry for JEE Main

Question

Amongst the following elements (whose electronic configurations are given below), the correct increasing order of ionization energy is (1) \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{1}\) (2) \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{3}\) (3) \([\mathrm{Ne}] 3 \mathrm{~s}^{2} 3 \mathrm{p}^{2}\) (4) \([\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^{2} 4 \mathrm{p}^{3}\) (a) \(3<\mathrm{k}<2<4\) (b) \(4<2<3<1\) (c) \(\mathrm{k}<3<4<2\) (d) \(2<4<1<3\)

Step-by-Step Solution

Answer

The correct order is (d) 2 < 4 < 1 < 3.

Step 1: Understand Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. Generally, elements with a stable electronic configuration have higher ionization energies.

Step 2: Analyze Element 1

Element 1 has the electronic configuration \([ ext{Ne}] 3s^2 3p^1\), which corresponds to Aluminum (Al). Its ionization energy is relatively low as it has only one p-electron which is easy to remove.

Step 3: Analyze Element 2

Element 2 is \([ ext{Ne}] 3s^2 3p^3\), which matches Phosphorus (P). With a half-filled p-subshell, its ionization energy is higher due to increased stability.

Step 4: Analyze Element 3

Element 3 is \([ ext{Ne}] 3s^2 3p^2\), corresponding to Silicon (Si). It has a slightly higher ionization energy than Aluminum, but less than Phosphorus, due to less stability in the p subshell than P.

Step 5: Analyze Element 4

Element 4 with configuration \([ ext{Ar}] 3d^{10} 4s^2 4p^3\) is Arsenic (As). Its ionization energy will be higher than Group 3 elements like Al, though lower than Phosphorus, due to a filled d subshell causing lower repulsion.

Step 6: Order the Elements by Ionization Energy

From these analyses, the increasing order of ionization energy is determined. Aluminum (1) < Silicon (3) < Arsenic (4) < Phosphorus (2).

Key Concepts

Electronic Configuration

The electronic configuration of an element is a description of how electrons are distributed within the atom's orbitals. Electrons are arranged in specific ways dictated by quantum mechanics principles. Each electron in an atom occupies the lowest energy orbital available, following the Aufbau principle. The configurations are filled following the order of increasing energy levels and subshells.

An example is Aluminum (Al) with an electronic configuration of \([ ext{Ne}] 3s^2 3p^1\), indicating that it uses the configuration of Neon plus additional electrons in the 3s and 3p orbitals. This tells us about its position on the periodic table and its chemical behavior. Understanding electronic configurations helps explain why elements react and bond in certain ways.

• Electronic configuration dictates how an element interacts chemically.
• Following the Aufbau principle helps in piecing these configurations together.
• The configuration assists in predicting element properties, such as ionization energy.

Periodic Table

The periodic table is a systematic arrangement of elements in order of increasing atomic number. It's more than just a table; it's a powerful tool that organizes elements by repeating chemical properties and trends. Each row in the periodic table is called a period, and each column is called a group.

The electronic configuration of elements helps locate them on the periodic table. For instance, elements with similar electronic configurations are placed in the same group, displaying similar properties. Aluminum, Silicon, and Phosphorus, located in the same period, exhibit a trend of increasing ionization energies as you move across the table.

• Each element position relates to its atomic structure and properties.
• It provides insight into element stability, reactivity, and behavior.
• Recognizing patterns in the table helps in understanding trends like ionization energy.

Chemical Stability

Chemical stability refers to the likelihood of an element or compound to maintain its original state over time. This stability is often determined by how full or satisfied an atom's electron shells and subshells are.

An atom with a full outer shell, similar to noble gases, is especially stable. When an electron configuration fills or half-fills a subshell, the atom experiences increased stability, such as phosphorus with its half-filled \(3p\) subshell. This suggests that it would require more energy to remove an electron, hence a higher ionization energy.

• Full or half-filled orbitals signify chemical stability.
• Stable configurations lead to higher ionization energies.
• Stability echoes in an element's resistance to losing electrons.

Element Analysis

Element analysis involves examining an element's electronic configuration and position on the periodic table to predict physical and chemical properties. This analysis helps explain phenomena such as ionization energy trends.

Through element analysis, we understand why Phosphorus has a higher ionization energy compared to Aluminum and Silicon. Phosphorus’s half-filled \(3p\) subshell makes it more stable, hence requiring more energy for electron removal. Similarly, by analyzing Arsenic’s configuration, we can deduce that the presence of a filled \(3d\) subshell influences its ionization energy by reducing electron-electron repulsion.

• Element analysis marries electronic configuration with observed trends on the periodic table.
• It explains differences in properties such as ionization energy among elements.
• Helps in predicting the order of elements based on electronic and chemical characteristics.