Question

Ionisation energies of fluorine and neon in \(\mathrm{KJ} / \mathrm{Mole}\) units are given respectively by: (a) 1681,1681 (b) 2081,2081 (c) 1681,2081 (d) 2081,1681

Short answer

The correct option is (c) 1681,2081.

Step-by-step solution

Understand Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion in its gaseous state. Different elements have different ionization energies due to their electron configurations and nuclear charge.

Analyze Given Options

We are given four options, each presenting two ionization energies. The task is to match the correct ionization energy with the given elements: fluorine and neon.

Apply Periodic Table Knowledge

In the periodic table, as you move from left to right, ionization energy generally increases because the effective nuclear charge increases, pulling electrons more strongly. Fluorine has an atomic number of 9, while neon has an atomic number of 10, placing it further to the right in the periodic table.

Identify Typical Ionization Energies

Neon, being a noble gas with a complete octet, will have a higher ionization energy compared to fluorine. Typical ionization energy values are around 1681 KJ/mol for fluorine and 2081 KJ/mol for neon.

Match the Values to Elements

Based on their typical ionization energies, we can match 1681 KJ/mol to fluorine and 2081 KJ/mol to neon. Therefore, the correct answer based on the values and element characteristics is (c) 1681,2081.

Key concepts

Periodic Table

The periodic table is a systematic arrangement of elements in order of increasing atomic number. Each element is placed in a specific position based on its properties and recurring chemical characteristics. The table is organized into groups and periods, which help in predicting the behavior of elements based on their position.

• Group: Vertical columns in the periodic table where elements have similar chemical properties.
• Period: Horizontal rows where properties of elements progressively change across the table.

As we move across a period from left to right, ionization energy generally increases because electrons are added to the same energy level while protons are added to the nucleus. This leads to a stronger attraction between the nucleus and electron cloud, requiring more energy to remove an electron. Understanding these patterns in the periodic table is crucial for predicting element reactivity and behavior.

Atomic Number

The atomic number of an element is the number of protons present in the nucleus of an atom. It is a unique identifier for each element and determines the element's identity and its position on the periodic table. The atomic number also indicates the number of electrons in a neutral atom, as the number of electrons equals the number of protons.

• The atomic number is symbolized by Z.
• For example, fluorine has an atomic number of 9, and neon has an atomic number of 10.

This concept is vital for understanding chemical properties and trends, such as ionization energy. With increasing atomic number, elements generally experience stronger nuclear attraction, influencing ionization energy. For elements like fluorine and neon, their atomic numbers help explain their positions and behaviors in the periodic table.

Noble Gases

Noble gases are elements found in Group 18 of the periodic table. They are characterized by their full valence electron shells, making them very stable and largely non-reactive. These gases include helium, neon, argon, krypton, xenon, and radon.

• Stability: Noble gases have complete outer electron shells, which gives them a natural stability and a low tendency to form chemical bonds.
• Ionization Energy: Since removing an electron from a full shell requires significant energy, noble gases have high ionization energies compared to other elements.

Neon, a noble gas with a completed octet, has a higher ionization energy than fluorine because of its stable electron configuration. This quality of noble gases justifies the high energy required to remove electrons, highlighting their unique position on the periodic table.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals. It provides insight into the chemical behavior of an element. Electrons are arranged around the nucleus in shells and subshells (s, p, d, f), following the Pauli exclusion principle and Hund's rule.

• Fluorine: 1s² 2s² 2p⁵ - Seven valence electrons and is one electron short of having a full outer shell.
• Neon: 1s² 2s² 2p⁶ - Has a complete octet in its outer shell, creating a stable electron configuration.

The electron configuration affects an element's ionization energy. Fluorine, being eager to complete its outer shell, has a lower ionization energy compared to neon, which already has a stable configuration. This disparity demonstrates how electron configurations play a key role in the elements' chemical properties and interactions.