Problem 30 - Chemistry and Chemical Reactivity

Question

Arrange the following atoms in order of increasing ionization energy: \(\mathrm{Li}, \mathrm{K}, \mathrm{C},\) and \(\mathrm{N}\)

Step-by-Step Solution

Answer

K, Li, C, N

Step 1: Understand Ionization Energy

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. It generally increases across a period and decreases down a group in the periodic table.

Step 2: Locate the Elements on the Periodic Table

Identify the positions of the elements: Lithium (Li) and Potassium (K) are in Group 1, while Carbon (C) and Nitrogen (N) are in Group 14 and 15, respectively. Li and K are in periods 2 and 4, whereas C and N are in period 2.

Step 3: Assess Periodic Trends

Since ionization energy increases across a period and decreases down a group, we expect K (further down in the same group as Li) to have a lower ionization energy than Li. In the same period, atomic number increases to the right, thus C has lower ionization than N.

Step 4: Compare and Arrange

Based on periodic trends: K < Li < C < N, where K has the lowest and N has the highest ionization energy among the given elements.

Key Concepts

Periodic Table

The periodic table is a systematic arrangement of elements in an ordered layout that highlights recurring chemical properties. Elements are organized in rows called periods and columns known as groups. This organization allows scientists and students to easily identify relationships between different elements and predict properties such as ionization energy.
For example:

• Elements in the same group have similar chemical properties due to the same number of valence electrons.
• Moving horizontally across a period, the atomic number increases, meaning each element has one more proton and electron than the previous one.
• Elements that sit farther down a group in the table generally have more electron shells.

Understanding the layout of the periodic table is crucial for predicting changes in ionization energy among other properties.

Periodic Trends

Periodic trends describe how certain properties of elements change as you move across the periodic table. One such trend is ionization energy, which refers to the energy needed to remove an electron from an atom in the gaseous state.
Crucial features of periodic trends include:

• Ionization energy generally increases as you move from left to right across a period due to the increased nuclear charge pulling electrons closer to the nucleus.
• Ionization energy tends to decrease down a group because the added electron shells create a greater distance between the nucleus and the outermost electrons, reducing nuclear pull.

Recognizing these trends is essential in understanding the varied behaviors of elements, and predicting ionization energy differences based on the elemental positions in the periodic table.

Electron Configuration

Electron configuration details the distribution of electrons in an atom's orbitals and significantly influences the atom's chemical properties, including ionization energy.
Key concepts of electron configuration that affect ionization energy include:

• Electrons fill orbitals starting from the lowest energy level moving up, following the Aufbau principle.
• An atom with a filled or half-filled orbital is more stable, which often means higher ionization energy.
• The more electrons in the outer shell, the further they are from the nucleus and the easier they are to remove, affecting ionization energy.

By understanding electron configurations, we can rationalize why it's harder or easier to remove an electron from certain elements, which ties directly back to their position on the periodic table and observed periodic trends.