Question

The correct order of second ionization potential of carbon, nitrogen, oxygen and fluorine is: (a) \(O>N>F>C\) (b) \(O>F>N>C\) (c) \(\mathrm{F}>\mathrm{O}>\mathrm{N}>\mathrm{C}\) (d) \(\mathrm{C}>\mathrm{N}>\mathrm{O}>\mathrm{F}\)

Short answer

The correct order is (c) \( \mathrm{F} > \mathrm{O} > \mathrm{N} > \mathrm{C} \).

Step-by-step solution

Understanding Ionization Potential

Ionization potential (IP) is the energy required to remove an electron from an atom or ion in the gaseous state. The second ionization potential is the energy needed to remove the second electron. The general trend is an increase in IP across a period due to increasing nuclear charge.

Apply General Trends

Across a period from left to right, the second ionization energy generally increases because atoms have a higher effective nuclear charge and smaller radii. From this trend, we can estimate that fluorine will have a higher IP compared to the others.

Consider Electron Configuration

The second ionization energy depends on the electronic configuration after removing one electron. Removing one electron from an atom like carbon results in a stable configuration, while for nitrogen, removing an electron disrupts a stable half-filled p sub-shell, making its second IP relatively lower than expected.

Compare Based on Stability After Second Ionization

Fluorine, after losing one electron, tends to achieve a stable configuration, thus requiring more energy to remove the second electron. Oxygen would have a higher second IP compared to nitrogen because removing electrons from a half-filled p-orbital is relatively less stable.

Key concepts

Second Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion in its gaseous state. It's a crucial concept in chemistry, as it helps us understand the reactivity and chemical behavior of elements. The second ionization energy specifically refers to the energy needed to remove a second electron after the first has already been removed. This energy is generally higher than the first ionization energy because removing an additional electron after the first makes the ion more positively charged, thereby increasing the electrostatic forces that must be overcome.

Several factors affect the second ionization energy:

• Electron configuration after the first electron is removed
• The resulting stability of the electron configuration
• The higher effective nuclear charge on the remaining electrons

Understanding this concept helps to explain why elements such as nitrogen and oxygen have distinct behaviors and trends in their ionization energies.

Periodic Trends

Periodic trends are patterns observed in the periodic table that reveal changes in the properties of elements. These trends help in predicting chemical properties and understanding the reactivity of the elements:

• Ionization Energy: Generally increases across a period (left to right) due to higher nuclear charges reducing atomic radii.
• Electronegativity: Also tends to increase as you move across a period for similar reasons.
• Atomic Radius: Decreases across a period as additional electrons are added to the same energy level, increasing the effective nuclear charge without significantly increasing electron shielding.

When discussing second ionization energies, these periodic trends are crucial. As elements like carbon, nitrogen, oxygen, and fluorine move from left to right across a period, their second ionization energies generally increase due to changes in nuclear charge and electron configuration.

Atomic Structure

The atomic structure of an element is defined by its protons, neutrons, and electrons. The arrangement of these subatomic particles dictates many chemical properties:

• Nucleus: Contains positively charged protons and neutral neutrons.
• Electron Orbitals: Electrons are arranged in specific orbitals and energy levels.

For ionization energy, the most significant part of atomic structure is how tightly electrons are bound to the nucleus. As electrons are negatively charged and protons positively charged, the more protons in the nucleus, the stronger the attraction for each electron. However, electron-electron repulsions and the distribution of electrons among orbitals (shells and sub-shells) also play a pivotal role. Understanding the atomic structure aids in explaining why elements like nitrogen have different ionization energies compared to oxygen or fluorine.

Electron Configuration

Electron configuration gives us insight into the distribution and arrangement of electrons in an atom's electron shells and subshells. The configuration is crucial for understanding an element's chemical properties:

• Determines the overall stability of the atom or ion after ionization.
• Affects how elements react and bond with others.

When examining second ionization energies, electron configuration helps explain why some elements, like oxygen, have higher ionization energies compared to others like nitrogen. After the first ionization, the electron configuration is altered, impacting the stability and energy required to remove a second electron. Elements may achieve full or half-full sub-levels, which are considered stable and thus require more energy for further ionization.