Problem 97 - A Complete Resource Book in Chemistry for JEE Main

Question

Which ionization potential in the following equations involves the greatest amount of energy? (a) \(\mathrm{Na} \longrightarrow \mathrm{Na}^{+}+\mathrm{e}^{-}\) (b) \(\mathrm{K} \longrightarrow \mathrm{K}^{+} \mathrm{e}^{-}\) (c) \(\mathrm{Cs}^{2+} \longrightarrow \mathrm{Cs}^{3+}+\mathrm{e}^{-}\) (d) \(\mathrm{Ca}^{+} \longrightarrow \mathrm{Ca}^{2+}+\mathrm{e}^{-}\)

Step-by-Step Solution

Answer

The ionization potential for Cs²⁺ to Cs³⁺ (option c) involves the greatest amount of energy.

Step 1: Understand Ionization Potential

Ionization potential is the energy required to remove an electron from a gaseous atom or ion. Higher ionization potential means higher energy required to remove an electron.

Step 2: Analyze the Equations

We need to compare the energy required for each ionization in the given equations: (a) Na to Na⁺, (b) K to K⁺, (c) Cs²⁺ to Cs³⁺, and (d) Ca⁺ to Ca²⁺. Each step represents the removal of an electron from a specific atom or ion.

Step 3: Consider the Charge of Ions

Removing an electron from a positively charged ion requires more energy than from a neutral atom due to the increased nuclear attraction. Therefore, ionizations involving higher positive charges typically require more energy.

Step 4: Compare the Ionization Energy Requirements

(a) involves one electron removal from neutral sodium. (b) involves one electron removal from neutral potassium. (c) involves removing an electron from Cs²⁺, already highly charged. (d) involves removing an electron from Ca⁺, a lower charge than Cs²⁺.

Step 5: Determine the Greatest Ionization Potential

Since Cs²⁺ (c) is the most positively charged of the initial states and generally requires more energy to remove an electron, the ionization of Cs²⁺ to Cs³⁺ involves the greatest energy among the options.

Key Concepts

Ionization Energy

Ionization energy is a fundamental concept in chemistry that refers to the amount of energy needed to remove an electron from an atom or ion in its gaseous state. In simpler terms, it tells us how tightly an electron is held within an atom. The larger the ionization energy, the more difficult it is to remove an electron.

Understanding ionization energy is crucial when studying the reactivity of elements. Generally:

• Metals tend to have lower ionization energies, making it easier for them to lose electrons and form positive ions.
• Nonmetals often have higher ionization energies, meaning they hold onto their electrons more tightly.

Several factors influence ionization energy, such as:

• The charge of the nucleus: A larger positive charge means stronger attraction to electrons.
• The distance of the outermost electrons from the nucleus: Greater distance generally lowers ionization energy.
• Electron shielding: Inner electron shells can shield outer electrons from the nucleus, affecting ionization energy.

Each of these factors plays a role in determining how much energy is needed to ionize an element.

Electron Removal

Electron removal refers to the process of taking away an electron from an atom or ion. This process is central to ionization, as it involves changing a neutral atom into a charged ion or increasing the positive charge of an already positive ion.

Removing an electron requires energy because electrons are naturally attracted to the nucleus due to opposite charges. Several key points about electron removal include:

• This process results in the formation of cations, which are positively charged ions.
• The energy required for electron removal varies depending on the initial charge of the atom or ion.
• More energy is needed to remove an electron from a positively charged ion compared to a neutral one, due to increased attraction to the nucleus.

Understanding the details of electron removal helps in predicting the behavior of elements during chemical reactions, especially those involving redox processes.

Nuclear Attraction

Nuclear attraction is the force that holds electrons around the nucleus of an atom. It is a crucial factor in understanding ionization energy and the removal of electrons. The nucleus is positively charged, containing both protons and neutrons, with protons being the carriers of this positive charge.

Electrons, which are negatively charged, are drawn towards the nucleus due to this attraction. Some important aspects of nuclear attraction include:

• It plays a significant role in the chemical characteristics of elements.
• The more positive charges present in the nucleus, the stronger the nuclear attraction, leading to higher ionization energy.
• As the number of electron shells increases, the outer electrons experience less nuclear attraction due to the shielding effect.

Understanding nuclear attraction is fundamental to explaining why it's more energy-intensive to remove an electron from ions with higher positive charges than from neutral atoms.

Ionization State

The ionization state of an atom or ion refers to its current charge after losing or gaining electrons. In chemical equations, this state is indicated by the charges beside elements or compounds. With each electron removal, the positive charge of the ion increases.

The ionization state is significant because it dictates how much energy is needed to remove further electrons:

• As the positive charge increases, it becomes progressively harder to remove more electrons due to stronger nuclear attractions.
• Higher ionization states correspond to elements that have lost more electrons.
• The ionization state helps predict how an element will interact during chemical reactions, particularly in ionic bonding.

Understanding ionization states helps in grasping how substances like metals and nonmetals will behave when they come into contact with each other, influencing everything from basic chemistry to advanced material science.