Ionic Bonding - Online Tutor, Practice Problems & Exam Prep

Chemical bonding involves attractive forces that hold atoms or ions together, leading to ionic compounds formed from cations and anions. Metals lose electrons, becoming cations, while nonmetals gain electrons, forming anions. This electron transfer results in compounds like NaCl. Ionic compounds exhibit distinct properties: they are solid at room temperature, have high melting and boiling points, conduct electricity when dissolved, and are hard yet brittle due to the strong ionic bonds between oppositely charged ions.

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 going to say, it's an attractive force between the opposing charges of 2 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 going to say metals tend to lose their valence electrons and nonmetals tend to gain electrons. We're going to 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 going to say that sodium loses an electron because it's in group 1a, it wants to be plus 1. So it's 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 cause 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 mentioned 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 we have in this example 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 affects 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 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, and the nonmetal exists as an anion. Their opposing charges are what caused them to combine together to give us sodium chloride, NaCl. So 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. So 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 composed of a metal and a nonmetal. What's most similar to that is potassium bromide. Potassium bromide, KBr, is also composed of 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 a metal losing electrons to become a positively charged ion (cation) and a nonmetal gaining those electrons to become a negatively charged ion (anion). The electrostatic attraction between these oppositely charged ions forms a strong bond, resulting in an ionic compound. 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 to form the ionic compound NaCl.

What are the key properties of ionic compounds?

Ionic compounds exhibit several distinct properties due to the strong electrostatic forces between their ions. They are typically solid at room temperature and have high melting and boiling points. This is because a significant amount of energy is required to break the strong ionic bonds. Ionic compounds are also good conductors of electricity when dissolved in water, as the ions are free to move and carry an electric current. Additionally, they are hard but brittle; they can withstand pressure but will crack or shatter if struck with a hammer. These properties are a direct result of the strong attraction between the oppositely charged ions in the compound.

How do metals and nonmetals form ionic bonds?

Metals and nonmetals form ionic bonds through the transfer of electrons. Metals, which are typically found on the left side of the periodic table, tend to lose their valence electrons to achieve a stable electron configuration, becoming positively charged cations. Nonmetals, found on the right side of the periodic table, tend to gain electrons to fill their valence shell, becoming negatively charged anions. For instance, sodium (a metal) loses one electron to become Na⁺, while chlorine (a nonmetal) gains that electron to become Cl⁻. The resulting Na⁺ and Cl⁻ ions attract each other due to their opposite charges, forming the ionic compound NaCl.

Why do ionic compounds have high melting and boiling points?

Ionic compounds have high melting and boiling points because of the strong electrostatic forces between the oppositely charged ions. These forces, known as ionic bonds, require a significant amount of energy to break. In an ionic lattice, each ion is surrounded by ions of the opposite charge, creating a very stable and tightly bound structure. To melt or boil an ionic compound, enough energy must be supplied to overcome these strong attractions, resulting in the high melting and boiling points observed in ionic compounds.

How does the structure of ionic compounds affect their physical properties?

The structure of ionic compounds significantly affects their physical properties. The strong electrostatic attraction between the cations and anions in an ionic lattice results in a solid state at room temperature. This structure also contributes to their high melting and boiling points, as a lot of energy is needed to break the ionic bonds. Additionally, when dissolved in water, the ions become free to move, making the solution a good conductor of electricity. The rigid and orderly arrangement of ions also makes ionic compounds hard but brittle; they can resist force to some extent but will shatter if struck sharply due to the alignment of like charges repelling each other when the structure is disturbed.