Question

The element with the highest first ionization potential is: (a) Nitrogen (b) Oxygen (c) Boron (d) Carbon

Short answer

Nitrogen has the highest first ionization potential.

Step-by-step solution

Understand Ionization Potential

The first ionization potential (energy) is the amount of energy required to remove the outermost electron from a neutral atom in its gaseous state. Generally, ionization energy increases across a period from left to right due to increased nuclear charge and decreases down a group as the outer electrons are farther from the nucleus.

Compare Elements in the Same Period

Among the given elements: Nitrogen, Oxygen, Boron, and Carbon, all except Boron are in the same period (2nd row) of the periodic table. Generally, ionization energy increases from left to right across a period due to decreasing atomic radius and increased effective nuclear charge.

Consider Atomic Structure

Boron (B), Carbon (C), and Oxygen (O) have one less electron than Nitrogen (N) in the p orbital. Nitrogen has a half-filled p orbital, which gives it added stability and higher ionization energy than Boron, Carbon, and even Oxygen, which due to electron-electron repulsion in the 2p sublevel, has a slightly lower ionization energy than Nitrogen.

Assess Exceptions to the Rule

Although Oxygen comes after Nitrogen in the period and would be expected to have a higher ionization potential, the repulsion between paired electrons in one of Oxygen's p orbitals makes it easier to remove one, resulting in Oxygen having a lower ionization potential than Nitrogen.

Conclusion

Based on the analysis and typical behavior of elements within the same period, Nitrogen, having a half-filled p subshell, has the highest first ionization potential among the given options.

Key concepts

Periodic Table Trends

Understanding periodic table trends is crucial for predicting the behavior of elements, including their ionization energies. As you move from left to right across a period on the periodic table, elements generally exhibit an increase in ionization energy. This trend occurs because the elements have more protons in the nucleus, leading to a stronger attraction between the nucleus and the electrons. This stronger attraction requires more energy to remove an electron. The atomic radius also generally decreases across a period, which contributes to the increase in ionization energy. Conversely, as you move down a group, ionization energy decreases. This is because the added electron shells increase the distance between the nucleus and the outermost electrons, reducing the nuclear pull and making it easier to remove an electron.

Electron Configuration

Electron configuration refers to the arrangement of electrons in an atom's orbitals. This arrangement is crucial for determining an element's chemical behavior and properties such as ionization energy. Electrons fill orbitals starting from the lowest energy level to higher ones, following a specific order often summarized by the aufbau principle:

• 1s holds 2 electrons
• 2s holds 2 electrons
• 2p holds 6 electrons

Nitrogen's electron configuration is 1s² 2s² 2p³. This half-filled 2p sublevel provides extra stability, contributing to its high ionization energy. Oxygen, just one element further in the period, has an electron configuration of 1s² 2s² 2p⁴. The 2p orbitals have paired electrons that experience repulsion, making it slightly easier to remove an electron compared to nitrogen.

Ionization Energy Comparisons

Ionization energy is the energy needed to detach an electron from an atom. Comparing the ionization energies of elements such as nitrogen and oxygen reveals important insights about atomic structure and periodic trends. Nitrogen has a higher first ionization energy than oxygen despite coming before oxygen in the periodic table. This anomaly arises because nitrogen's half-filled 2p orbital is more stable than the partially filled 2p orbital of oxygen, which has electron repulsions that reduce its ionization energy. Understanding such exceptions is vital for accurately predicting elements' reactivity and chemical properties.

Noble Gas Configuration

A noble gas configuration is achieved when the orbitals fill up to create a full valence shell, mimicking the electron configuration of noble gases. This full valence shell provides stability, making these elements famously unreactive. Noble gases have high ionization energies, reflecting their reluctance to lose electrons and break this stable configuration. Elements tend to gain, lose, or share electrons to achieve a noble gas configuration. For example, when discussing ionization energy, note that elements strive for stability akin to noble gases, indicating higher ionization energies especially when moving toward achieving a noble gas configuration. However, elements like nitrogen are stable in their half-filled p configuration and thus have higher ionization energies reflective of their stable state, even without a complete noble gas configuration.