Question

Often the minerals we need in our diet are provided to us in vitamin tablets as cations. Following is a list of ingredients for a vitamin and mineral supplement. The table below highlights some of these minerals and identifies the ion provided for each mineral. Determine the number of protons and electrons in each of these ions. $$ \begin{array}{|l|l|c|l|l|} \hline {\text { Mineral supplement }} & {\text { Mineral use }} & \text { Ion provided } & \text { Number of protons } & \text { Number of electrons } \\ \hline \text { Calcium carbonate } & \text { Bones and teeth } & \mathrm{Ca}^{2+} & & \\ \hline \text { Iron(II) sulfate } & \text { Hemoglobin } & \mathrm{Fe}^{2+} & & \\ \hline \text { Chromium(III) nitrate } & \text { Insulin } & \mathrm{Cr}^{3+} & & \\ \hline \text { Magnesium sulfate } & \text { Bones } & \mathrm{Mg}^{2+} & & \\\ \hline \text { Zinc sulfate } & \text { Cellular metabolism } & \mathrm{Zn}^{2+} & & \\ \hline \text { Potassium iodide } & \text { Thyroid function } & \mathrm{I}^{-} & & \\ \hline \end{array} $$

Short answer

Calcium (Ca): 20 protons, 18 electrons; Iron (Fe): 26 protons, 24 electrons; Chromium (Cr): 24 protons, 21 electrons; Magnesium (Mg): 12 protons, 10 electrons; Zinc (Zn): 30 protons, 28 electrons; Iodine (I): 53 protons, 54 electrons.

Step-by-step solution

Identify the Element and Ion Charge

First, identify the element of each mineral supplement and its ionic charge. The element can be found using the periodic table, and the ionic charge is given in the table.

Determine the Number of Protons

Use the periodic table to find the atomic number of each element, which corresponds to the number of protons in a neutral atom of that element.

Determine the Number of Electrons in the Ion

In a neutral atom, the number of electrons equals the number of protons. For ions, adjust the number of electrons according to the charge: subtract the charge for cations (positive ions), and add the charge for anions (negative ions).

Complete the Table for Calcium (Ca)

The atomic number of calcium is 20, so a neutral calcium atom has 20 protons and 20 electrons. The \(\mathrm{Ca}^{2+}\) ion has lost 2 electrons, so it has 18 electrons.

Complete the Table for Iron (Fe)

The atomic number of iron is 26, so a neutral iron atom has 26 protons and 26 electrons. The \(\mathrm{Fe}^{2+}\) ion has lost 2 electrons, so it has 24 electrons.

Complete the Table for Chromium (Cr)

The atomic number of chromium is 24, so a neutral chromium atom has 24 protons and 24 electrons. The \(\mathrm{Cr}^{3+}\) ion has lost 3 electrons, so it has 21 electrons.

Complete the Table for Magnesium (Mg)

The atomic number of magnesium is 12, so a neutral magnesium atom has 12 protons and 12 electrons. The \(\mathrm{Mg}^{2+}\) ion has lost 2 electrons, so it has 10 electrons.

Complete the Table for Zinc (Zn)

The atomic number of zinc is 30, so a neutral zinc atom has 30 protons and 30 electrons. The \(\mathrm{Zn}^{2+}\) ion has lost 2 electrons, so it has 28 electrons.

Complete the Table for Iodine (I)

The atomic number of iodine is 53, so a neutral iodine atom has 53 protons and 53 electrons. The \(\mathrm{I}^{-}\) ion has gained 1 electron, so it has 54 electrons.

Key concepts

Atomic Number

The atomic number is a fundamental property of an element and is key to understanding the structure of atoms in chemistry. It is denoted on the periodic table and represents the number of protons present in the nucleus of an atom. Since atoms are electrically neutral, the atomic number also indicates the number of electrons in a neutral atom. For example, calcium has an atomic number of 20, which means a neutral calcium atom contains 20 protons and 20 electrons.

In the context of mineral supplements, identifying the atomic number is the first step to figuring out the makeup of the ions present. This essential piece of information allows us to understand how the elements will interact in the body, such as aiding in the development of bones and teeth or contributing to metabolic processes.

Protons and Electrons in Ions

When an atom loses or gains electrons, it becomes an ion. The number of protons in an atom remains constant, as this defines the element itself. However, the number of electrons can change, leading to a positive or negative charge on the ion. A cation, which is a positively charged ion, has more protons than electrons. Conversely, an anion, a negatively charged ion, has fewer protons than electrons.

For instance, when we look at \(\mathrm{Fe}^{2+}\), this signifies an iron ion with a 2+ charge, indicating it has lost 2 electrons. Given iron's atomic number is 26, a neutral iron atom would have 26 electrons. Therefore, the \(\mathrm{Fe}^{2+}\) ion will have 24 electrons. Similarly, \(\mathrm{I}^{-}\), an anion, has gained an extra electron in comparison to a neutral iodine atom, leading to a total of 54 electrons.

Cation and Anion Charges

The charge on an ion is critical because it determines the ion's chemical properties and how it will interact with other substances. Cations, like \(\mathrm{Ca}^{2+}\), \(\mathrm{Fe}^{2+}\), and \(\mathrm{Mg}^{2+}\), have more protons than electrons and are formed when an atom loses one or more electrons, resulting in a net positive charge. These cations are essential in biology and are found in many dietary supplements.

Anions, on the other hand, are negatively charged ions that have gained one or more electrons. The \(\mathrm{I}^{-}\) in potassium iodide is a great example of an anion. While cations typically aid in muscle contraction and nerve transmission, anions often help in balancing fluids and transporting energy. Understanding the charges of ions in mineral supplements helps predict how they will behave within the body, such as their solubility and their ability to conduct electricity in bodily fluids.