Question

Without looking at data in the text, sketch a qualitative graph of the third ionization energy versus atomic number for the elements Na through Ar, and explain your graph.

Short answer

To create a qualitative graph of the third ionization energy vs atomic number for elements Na through Ar, first, identify the atomic numbers of the respective elements (Na: 11, Mg: 12, Al: 13, Si: 14, P: 15, S: 16, Cl: 17, Ar: 18). Then, create a graph with atomic number on the x-axis and third ionization energy on the y-axis. Plot the trend: 1. Na and Mg have very high third ionization energies due to having only one or two valence electrons. 2. Al to P have a typical increasing trend in ionization energy from left to right. 3. S has a slight drop due to electron-electron repulsion in 3p orbitals. 4. Cl and Ar have a sharp increase due to breaking into a lower energy shell. Finally, sketch the graph capturing these trends and irregularities without focusing on the exact values.

Step-by-step solution

Identify the elements

First, let's identify the elements we will be working with. We need to sketch a graph for the elements sodium (Na) to argon (Ar). These elements are in the third period of the periodic table: - Sodium (Na), atomic number 11 - Magnesium (Mg), atomic number 12 - Aluminum (Al), atomic number 13 - Silicon (Si), atomic number 14 - Phosphorus (P), atomic number 15 - Sulfur (S), atomic number 16 - Chlorine (Cl), atomic number 17 - Argon (Ar), atomic number 18

Plan the graph layout

Next, we need to plan the layout of the graph. Since we are plotting the third ionization energy versus atomic number, we will have atomic number on the x-axis and the third ionization energy on the y-axis. We can label the x-axis with the atomic numbers (11 to 18) and the y-axis with arbitrary ionization energy values, remembering that this is a qualitative graph, so the exact values are not important.

Plot the trend

Now we need to plot the trend of the third ionization energy for these elements. We know that ionization energy generally increases from left to right across a period. However, since we are focusing specifically on the third ionization energy, we may notice a few irregularities in this trend. - For Na and Mg, the third ionization energy will be very high, as these elements only have one or two valence electrons, making it extremely difficult to remove the third electron. - For Al to P, the trend will be the typical increase in ionization energy as we move left to right across the period. - For S, there may be a slight drop in ionization energy due to electron-electron repulsions in the 3p orbitals. - Finally, for Cl and Ar, the ionization energy will increase sharply as removing the third electron requires breaking into a lower energy shell.

Sketch the graph

Now we can sketch the qualitative graph using the information from the previous steps. Begin by plotting the extremely high ionization energies for Na and Mg, followed by the general increasing trend for Al to P. Add a slight decrease for S and then a sharp increase for Cl and Ar to account for the lower energy shell. Remember, this graph is qualitative, so the most important aspect is capturing the trends and irregularities, not the exact values.

Key concepts

Ionization Energy Trend

When we talk about ionization energy, it refers to the amount of energy required to remove an electron from a neutral atom in its gaseous state. As you move from left to right across a period in the periodic table, the ionization energy generally increases. This occurs because the number of protons increases, which leads to a stronger attraction between the positively charged nucleus and the negatively charged electrons, making it harder to remove an electron.

However, the third ionization energy involves removing the third electron, which can introduce anomalies in this general trend. This is particularly notable in elements where removing a third electron means breaking into a more stable, lower energy electron shell, or where electron-electron repulsion plays a significant role.

Periodic Table

The periodic table is a tabular arrangement of elements organized by increasing atomic number. Each row represents a period, where elements are listed in order of their atomic numbers. As you move from one element to the next within a period, properties such as ionization energy gradually change.

For the elements sodium (Na) through argon (Ar) in the third period, we see these changes as we move from element to element. The table aids in predicting trends in elemental properties, such as those displayed in third ionization energies. Understanding where an element lies on the periodic table is crucial in hypothesizing its chemical behavior.

Atomic Number

The atomic number of an element is a fundamental property that indicates the number of protons in its atomic nucleus and, by extension, the number of electrons in a neutral atom. It is the ordering principle of the periodic table, denoting an element's position and allowing for the prediction of ionization energy trends.

The sequence of atomic numbers, such as 11 for Na through 18 for Ar, provides a framework for understanding why ionization energies generally increase across a period. Elements with higher atomic numbers within a period have more protons, thus exerting a greater nuclear charge on the electrons, increasing the ionization energy required to remove them.

Qualitative Graph

A qualitative graph displays the general pattern or trend of data rather than specific numerical values. In the context of a graph of the third ionization energy versus atomic number, it illustrates how ionization energy behaves as we move through elements Na to Ar.

Creating a qualitative graph requires us to conceptualize the relative changes in ionization energy. We don’t stress over exact values but rather focus on how the third ionization energy peaks at Na and Mg, trends upward from Al to P, dips slightly at S due to electron repulsion, and jumps again at Cl and Ar due to the stable electron configurations.

Electron-Electron Repulsion

Electron-electron repulsion refers to the force exerted by electrons on each other due to their negative charges. This repulsion can affect the ionization energy, particularly in subshells that are partially filled with electrons.

For example, in sulfur (S), the 3p subshell contains four electrons, creating repulsion that can slightly reduce the ionization energy compared to an element with a half-filled subshell, where electron repulsion is minimized. Recognizing electron-electron repulsion helps explain deviations from the expected ionization energy trend across a period.