Question

Give the charge each atom takes when it forms an ion. If more than one charge is possible, list both. a) \(\mathrm{Ca}\) b) I c) \(\mathrm{Fe}\)

Short answer

Ca: \( ext{Ca}^{2+} \), I: \( ext{I}^- \), Fe: \( ext{Fe}^{2+} \), \( ext{Fe}^{3+} \).

Step-by-step solution

Determine the Valence Electrons

To find the charge an atom takes when it forms an ion, first determine the number of valence electrons based on the element's group number in the periodic table. Calcium (Ca) is in Group 2, iodine (I) is in Group 17, and iron (Fe) is a transition metal.

Predict the Ion Charge for Calcium (Ca)

Calcium (Ca), with its 2 valence electrons, tends to lose these electrons to achieve a stable electron configuration similar to the nearest noble gas, argon. Therefore, when it forms an ion, calcium has a charge of \( +2 \), written as \( ext{Ca}^{2+} \).

Predict the Ion Charge for Iodine (I)

Iodine (I) has 7 valence electrons and needs one more to achieve the stable electron configuration of the nearest noble gas, xenon. Therefore, iodine often gains one electron when forming an ion and typically has a charge of \( -1 \), written as \( ext{I}^- \).

Predict the Ion Charges for Iron (Fe)

Iron (Fe) is a transition metal and can lose different numbers of electrons. Common charges for iron are \( +2 \) and \( +3 \), leading to the ions \( ext{Fe}^{2+} \) and \( ext{Fe}^{3+} \). These charges result from losing 2 or 3 electrons from its valence shell.

Summarize the Ion Charges

To conclude: Calcium forms \( ext{Ca}^{2+} \), iodine forms \( ext{I}^- \), and iron can form both \( ext{Fe}^{2+} \) and \( ext{Fe}^{3+} \). These charges are based on the loss or gain of electrons relative to achieving noble gas electron configurations.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom. These electrons play a crucial role in chemical bonding and ion formation. The number of valence electrons dictates how an atom will react and what kind of ions it will form. For most atoms, those valence electrons are generally involved in forming bonds. It is also important to note that the valence electrons are the electrons furthest away from the nucleus, making them more accessible for interactions.
To determine the valence electrons, examine the Group number on the periodic table. For example:

• Calcium (Ca) is in Group 2, so it has 2 valence electrons.
• Iodine (I) lies in Group 17 with 7 valence electrons.
• Transition metals like iron (Fe) have a more complex valence electron configuration which contributes to their varied charge states.

Understanding valence electrons helps predict the types of ions an atom may form. Atoms typically lose or gain electrons to achieve a noble gas electron configuration. This directly influences an atom's ion form.

Periodic Table Groups

Periodic table groups play a crucial role in predicting the behavior of elements, particularly in ion formation. Elements in the same group tend to display similar chemical properties, such as having the same number of valence electrons. This similarity helps in predicting the type and charge of ions an element will form.
Here are some key points about periodic table groups:

• Each group in the periodic table represents elements with the same number of valence electrons. For instance, all elements in Group 1 possess one valence electron.
• Group 2 elements, including calcium, have two valence electrons and often form ions with a charge of +2 by losing them.
• Group 17 elements, like iodine, typically have seven valence electrons and tend to gain one electron, forming ions with a -1 charge.
• Transition metals, often found in the central block of the periodic table, don't follow a strict pattern. They can exhibit various valence states due to the electrons in their d orbitals.

Knowing an element's group helps predict its chemical reactivity and its ability to form ions with other elements. This organization in the periodic table is essential for understanding chemical behavior.

Transition Metals

Transition metals are an intriguing class of elements often located in the center of the periodic table. These metals have unique properties compared to other elements due to their electron configurations. They generally have partially filled d orbitals, which allows them to exhibit a wide range of oxidation states in their compounds.
Here are some notable properties of transition metals:

• They can have multiple oxidation states. For instance, iron (Fe) commonly forms +2 and +3 ions, known as ferrous and ferric ions, respectively.
• The variable oxidation states arise because transition metals can lose electrons from both their outermost s and d subshells.
• These metals are often good conductors of electricity and heat and are known for their strength and durability.
• Due to their complex electron arrangement, transition metals can form colorful compounds and are often used in pigments and dyes.

The capability of transition metals to form various ions makes them extremely important in chemistry and industry. Their versatility in interactions is a key reason why they are extensively utilized in catalysis and in the formation of alloys.