Ionic Bonding: Study with Video Lessons, Practice Problems & Examples

Chemical bonding involves the attractive forces that hold atoms or ions together, leading to the formation of ionic compounds, or ionic salts. These consist of cations (positive ions) and anions (negative ions) that combine due to their opposing charges. Ionic compounds typically exist as solids at room temperature, exhibit high melting and boiling points, and are brittle yet hard. When dissolved in water, they conduct electricity well. Understanding these properties is essential for grasping the behavior of ionic compounds in various chemical contexts.

Ionic Bonding Concept 1

Now before we discuss ionic bonding, realize that chemical bonding in general is the attractive force that holds atoms or ions together in a chemical compound. These chemical bonds, that's when elements bond. They either share or transfer electrons to attain a filled outer shell like the noble gases. So that's chemical bonding in general. Now if we're looking at ionic compounds and by extension ionic bonding, we're going to say here that key features of ionic compounds, we're gonna say it's an attractive force between the opposing charges of two ions. So basically, when we say ionic compounds, we can also refer to them as ionic salts. These are compounds composed of a positive ion called a cation and a negative ion called an anion. Their opposite charges are what cause them to combine together to make my ionic compound. Now recall that we're gonna say metals tend to lose their valence electrons and nonmetals tend to gain electrons. We're gonna say ionic bond formation helps to lower the potential energies of that cation and the anion. So for example, we have sodium here, and we have chlorine here. We're gonna say that sodium loses an electron because it's in group 1A, it wants to be plus 1. So it has lost its electron, so now it's plus 1. Chlorine is in group 7A, which tends to be minus 1 in its charge. How is it minus 1? It just gained the electron that belonged to sodium, so gaining that electron now gives it a negative charge. Because they have opposing charges now, they're going to combine together to make my ionic compound or ionic solid. So that gives me NaCl. Now besides ionic compounds, we have what's called covalent compounds. These are another type of compounds composed of only nonmetals, and they'll be discussed later on. For now, just realize that when it comes to an ionic solid or ionic compound, it's fundamentally a positive ion called a cation connected to a negative ion called an anion. Their opposite charges are what causes them to be attracted to one another to help make our ionic compound/ionic solid.

Ionic Bonding Example 1

Here we're asked which of the following species has bonds with the most ionic character? So think about it. When we talk about ionic bonding, we said it's the opposing charges of a cation and an anion. Remember, the cation, which is positive, is usually a metal. It can also be the ammonium ion, and then remember our anion, our negative ion, will be a nonmetal. These are the fundamental definitions we talked about way back when we first covered ionic compounds versus covalent compounds. So if you don't remember that, it's a good idea to write this down. So basically the most ionic character will be the one that fits this definition of a cation bonded to an anion. So we're looking for an example that has either a metal connected to a nonmetal or the ammonium ion connected to a nonmetal. And if we look at our choices present, we see that the only choice has to be option c because here it has tin, which is Sn, a metal, connected to oxygen, a nonmetal. So in this example, we have a metal to a nonmetal. All the others don't fit the criteria to be an ionic compound because they're just nonmetals connected together. They themselves would just represent covalent compounds.

Ionic Bonding Concept 2

Now with ionic compounds, we have to take a look at their properties. We're going to say the strength of the attractive forces between the opposing ions directly affect the properties of ionic compounds. So here we can look at their physical states, their conductivity, their temperature, as well as their durability. Now we're going to say here that because of the way they are attracted to one another in terms of opposing charges, we're going to say they exist as solids at room temperature. In terms of conductivity, we can take an ionic solid and dissolve it within a solvent like water. This makes them good electrical conductors when dissolved. In terms of temperature, we're going to say ionic solids tend to have high melting points and high boiling points. And here's the thing, because of their opposing charges, it's positive ions connected to negative ions, we're going to say that they tend to be both hard but brittle. So they are hard, they feel hard when you hold them, but they're brittle, which means that if I take a hammer and I hit an ionic solid, it'll splinter and crack because of this brittle behavior. And again, that's because of their opposing charges. So when it comes to ionic solids, just realize that it'll affect their physical properties and form in terms of physical state, conductivity, temperature, and durability.

Ionic Bonding Example 2

Which of the following compounds has properties most similar to sodium chloride? Sodium chloride is composed of a metal and a nonmetal. The metal exists as a cation. The nonmetal exists as an anion. Their opposing charges are what cause them to combine together to form sodium chloride, NaCl. We have to look to see what else is similar to that. If we take a look, we're going to say that options a, b, and d are compounds composed of only nonmetals. We haven't gone into detail about them, but we know that compounds composed of only nonmetals are covalent compounds. NaCl, sodium chloride, is an ionic compound. It's composed of a metal and a nonmetal. What's most similar to that is potassium bromide. Potassium bromide, KBr, is also a metal and a nonmetal together. Because it is also an ionic compound, we'd expect it to have similar ionic compound properties like sodium chloride. So here, option c is the correct answer.

Here’s what students ask on this topic:

What is ionic bonding and how does it occur?

Ionic bonding is a type of chemical bonding that occurs when atoms transfer electrons to achieve a filled outer shell, similar to noble gases. This process involves the formation of ions: cations (positive ions) and anions (negative ions). Metals tend to lose electrons, becoming cations, while nonmetals gain those electrons, becoming anions. The electrostatic attraction between these oppositely charged ions results in the formation of an ionic bond. For example, in sodium chloride (NaCl), sodium (Na) loses one electron to become Na⁺, and chlorine (Cl) gains that electron to become Cl⁻. The resulting Na⁺ and Cl⁻ ions attract each other, forming the ionic compound NaCl.

What are the properties of ionic compounds?

Ionic compounds exhibit several distinct properties due to the strong electrostatic forces between their ions. They typically exist as solids at room temperature and have high melting and boiling points. This is because a significant amount of energy is required to break the ionic bonds. Ionic compounds are also hard but brittle; they can crack or shatter when struck. Additionally, when dissolved in water, ionic compounds dissociate into their constituent ions, making the solution a good conductor of electricity. These properties are a direct result of the strong attractions between the positive and negative ions in the compound.

How do ionic compounds conduct electricity?

Ionic compounds conduct electricity when they are dissolved in water or melted. In their solid state, the ions are fixed in place within a crystal lattice and cannot move freely, so they do not conduct electricity. However, when dissolved in water, the ionic bonds break, and the ions dissociate, becoming free to move. These free-moving ions can carry an electric current through the solution. Similarly, when an ionic compound is melted, the ions are no longer held in a rigid structure and can move freely, allowing the molten compound to conduct electricity.

Why are ionic compounds brittle?

Ionic compounds are brittle because of the nature of the ionic bonds and the arrangement of ions in a crystal lattice. When a force is applied to an ionic solid, it can cause the ions of like charge to be forced closer together. Since like charges repel each other, this repulsion can cause the crystal to shatter or crack. This brittleness is a result of the strong electrostatic forces that hold the ions in place; when these forces are disrupted, the structure breaks apart rather than deforming.

What is the difference between ionic and covalent compounds?

The primary difference between ionic and covalent compounds lies in how the atoms achieve stable electron configurations. In ionic compounds, atoms transfer electrons to form ions, which are then held together by electrostatic forces. These compounds typically form between metals and nonmetals. In contrast, covalent compounds form when atoms share electrons to achieve stability. This type of bonding usually occurs between nonmetals. Covalent compounds generally have lower melting and boiling points compared to ionic compounds and do not conduct electricity in any state. Additionally, covalent compounds can exist in various physical states (solid, liquid, or gas) at room temperature.