Question

Which ionic compound is expected to form from combining the following pairs of elements: (a) barium and fluorine, (b) cesium and chlorine, (c) lithium and nitrogen, (d) aluminum and oxygen?

Short answer

The ionic compounds formed from the given pairs of elements are: (a) BaF₂, (b) CsCl, (c) Li₃N, and (d) Al₂O₃.

Step-by-step solution

Identify the charges of the ions

Barium (Ba) is in Group 2, so it tends to form a +2 ion (Ba²⁺). Fluorine (F) is in Group 7 (also known as Group 17), so it tends to form a -1 ion (F⁻).

Combine the ions to form an ionic compound

To form a stable ionic compound, we need the charges to balance out. In this case, we will need two F⁻ ions to balance the charge of one Ba²⁺ ion. The ionic compound formed will be BaF₂. #b) Cesium and Chlorine#

Identify the charges of the ions

Cesium (Cs) is in Group 1, so it tends to form a +1 ion (Cs⁺). Chlorine (Cl) is also in Group 7 (Group 17), so it tends to form a -1 ion (Cl⁻).

Combine the ions to form an ionic compound

In this case, the charges of the ions are already balanced. We can directly combine one Cs⁺ ion with one Cl⁻ ion to form the ionic compound CsCl. #c) Lithium and Nitrogen#

Identify the charges of the ions

Lithium (Li) is in Group 1, so it tends to form a +1 ion (Li⁺). Nitrogen (N) is in Group 5 (Group 15), so it tends to form a -3 ion (N³⁻).

Combine the ions to form an ionic compound

We will need three Li⁺ ions to balance the charge of one N³⁻ ion. The ionic compound formed will be Li₃N. #d) Aluminum and Oxygen#

Identify the charges of the ions

Aluminum (Al) is in Group 13, so it tends to form a +3 ion (Al³⁺). Oxygen (O) is in Group 6 (Group 16), so it tends to form a -2 ion (O²⁻).

Combine the ions to form an ionic compound

In this case, we will need two Al³⁺ ions to balance the charge of three O²⁻ ions, giving us a compound ratio of 2:3. The ionic compound formed will be Al₂O₃.

Key concepts

Chemical Bonding

When atoms come together, they engage in different forms of chemical bonding to achieve stability. Ionic bonding is a type of chemical bond that involves the transfer of electrons between atoms. In this process, one atom loses one or more electrons, becoming a positively charged ion, while another atom gains those electrons, becoming a negatively charged ion. The electrostatic attraction between these oppositely charged ions holds them together, creating an ionic compound.
The formation of ionic compounds is typically observed between metals and non-metals. Metals, which are located on the left side of the periodic table, tend to lose electrons and form positive ions (cations). Non-metals, found on the right side, tend to gain electrons, becoming negative ions (anions). By understanding the nature of ionic bonds, we can predict how specific elements will combine to form compounds, like those in everyday substances such as table salt (NaCl).

• An ionic bond is formed by the transfer of electrons.
• Metals form cations by losing electrons.
• Non-metals form anions by gaining electrons.
• The attraction between ions holds the compound together.

Ion Charges

Ion charges are critical in determining how ionic compounds are formed. Each element has a tendency to lose or gain a specific number of electrons, which corresponds to its ion charge. These charges are often predictable based on an element's position in the periodic table.
Elements in Group 1 typically form a +1 charge because they lose one electron. Group 2 elements form a +2 charge, losing two electrons. For non-metals, the ion charges are generally negative. For instance, Group 17 elements tend to have a -1 charge because they gain one electron to achieve a full outer shell. Understanding these predictable charges helps in determining the ratios of ions needed to form neutral compounds.

• Group 1 elements form +1 ions.
• Group 2 elements form +2 ions.
• Group 17 elements typically form -1 ions.
• Ion charges must balance to create a stable compound.

Periodic Table Groups

The periodic table is organized into columns known as groups, which reflect the number of electrons in the outer shell of an atom for the main-group elements. These outer electrons, also known as valence electrons, play a key role in chemical bonding and determining ion charges.
Elements within the same group typically exhibit similar chemical behaviors. For instance, elements of Group 1, the alkali metals, all have one valence electron. This uniformity lends them a tendency to lose one electron and form +1 ions. Similarly, Group 17 elements, known as the halogens, have seven valence electrons and often form -1 ions by gaining an electron.
By understanding an element's group, we can predict not only the type of ion it will form but also how it might react with other elements. This knowledge of periodic table groups facilitates the understanding of chemical properties and bonding behavior.

• Group numbers indicate the number of valence electrons.
• Elements in the same group exhibit similar chemical properties.
• Group 1: Alkali metals - tend to form +1 ions.
• Group 17: Halogens - tend to form -1 ions.
• Understanding groups aids in predicting chemical reactions.