Core Concepts

In this tutorial about lattice energy, we will cover its definition, relevant periodic table trends, components that affect it, and how to calculation it.

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What is Lattice Energy?

During the development of hard ionic compounds, electropositive metals react v electronegative nonmetals. Both the generation and dissolution of together compounds indicate the ide of lattice energy, a form of potential energy expressed in units of kJ/mol. Lattice power maintains the resolved positions that cations and anions within ionic compounds. Us can further investigate this hatchet in two different ways, depending upon our perspective.

The vital to understanding this principle lies in the crystalline framework of ionic compounds. Their strong, rigid composition allows interactions in between each fee ion and its oppositely charged counterparts. These interactions involve huge amounts that energy, explaining the high melting and boiling points characteristic of ionic compounds.

Lattice power can be defined as a particular quantity of power is released when gaseous ion react during the development of one mole that a hard ionic compound; however, it likewise describes the power that facilitates the dissociation that one mole that a hard ionic compound into its constituent gaseous ions. Depending top top our favored definition, the lattice power of a offered ionic compound may either it is in a hopeful or an unfavorable value.

Exothermic matches Endothermic

We deserve to view lattice energies as either endothermic or exothermic processes relying on which meaning we emphasis on. A process is exothermic when it releases energy. Our very first definition, the formation of an ionic compound, entails exothermic lattice energy, matching to a an adverse value.

On the various other hand, if we usage the alternative definition, the dissolution of one ionic compound, the nature the the lattice power value changes. Since this process requires energy, it falls into the endothermic category, matching to a optimistic value.

Factors that affect Lattice Energy

1. The charges hosted by the constituent ions (represented through the variables Q1 and Q2)

As we rise the ion charge variable, lattice energy increases. This way that ion with bigger charge worths will create ionic link with better lattice energies. In turn, ion possessing weaker dues decrease the lattice energies of their compounds.

2. The distance in between the constituent ion (represented by the variable R)

As we rise the street variable, lattice power decreases. Essentially, larger ions create ionic link with smaller sized lattice energies as result of the increased distance in between them. Smaller ions produce larger lattice energies in your ionic compounds.

Lattice power Trends

To summarize, lattice power increases as we increase ion charge and also decrease the distance. More specifically, it rises from left come right throughout periods and from bottom to height up groups.

We can summarize lattice energy periodic table trends in the complying with image:


Finding Lattice Energies

When presented through multiple ionic compounds, chemistry must often determine which exhibits the highest lattice energy. To perform so, they consider both the ion fee variable and also the street variable.

Calculating Lattice Energies

Although calculating specific lattice energies can prove complicated, we regularly simplify the procedure using Coulomb’s Law. This law provides the following equation explicate the lattice energy of a offered ionic compound:

Q1 & Q2 = the family member charges of the constituent ion in an ionic compoundR = the distance between chargesK = 2.31 x 10^-19 J-nm.

The final answer should be created in units of Joules (J).

Steps come Solve:Solve the equation for each ionic compound, inputting the charge and also distance values certain to it.Compare the results; the largest quantity denotes the ionic compound with the biggest lattice energy.

Approximating Lattice Energies

During comparisons, we can likewise use the charge and distance variables to estimate loved one lattice energies.

Steps come Solve:

1. First look at the family member charges shown by each ion in a offered compound—if one compound has much greater ionic charges, then it will certainly likely have actually the greater lattice energy.

2. If the fee discrepancies between compounds carry out not it seems to be ~ clear, calculation Q1 x Q2 for each compound and also compare those values. For example, a calculated fee of -3 has 3 times the magnitude of a calculated fee of -1; this would signify that the ionic compound with the fee of -3 exhibits a much greater lattice energy than the ionic compound through the -1 charge (roughly 3 times together high).

3. If the fees of multiple compounds room the exact same or too similar in worth to develop distinctions, consider the sizes of the ions. Juxtapose atomic size, to compare cation to cation and anion come anion in between compounds. If you check out a significant discrepancy in dimension either between cations or in between anions, the component through the bigger atomic radius will reduced the lattice power of its corresponding compound. Vice versa, the ion with a smaller atomic radius will boost the power value the its particular compound.

Applications of Lattice Energy

The Born-Haber Cycle

Lattice power is implicated in the Born-Haber Cycle, which help chemists analyze reaction energies. This cycle generally informs investigations of ionic compound development from different elements. It clarifies the as whole reaction process by break it down right into a collection of steps. This method to chemistry reaction analysis stems indigenous Hess’s Law, which claims that overarching energy alters can be established by exploring individual steps, climate combining your effects.

As lattice power forms component of the Born-Haber cycle equation, we deserve to solve because that it as soon as the other factors are plugged in. The equation reads as follows:

Heat that formation= lattice power + heat of atomization + dissociation energy + (sum of Ionization energies) + (sum that electron affinities)

The Born-Haber Cycle applies Hess’s regulation to calculate lattice energies by juxtaposing a offered ionic compound’s enthalpy readjust of development to the enthalpy forced to kind gaseous ions from that components.

Other Applications the Lattice Energies

Scientists use lattice energies more broadly to evaluate electron relationships and fluoride relationships. The factors, in turn, educate investigations about the family member strengths of different ionic solids as well as predictions around ionic compound identities, components, and also properties.

Further Examples that Calculating Lattice Energies

Examples: utilizing Approximation Techniques

First, we will practice solving because that the charge variable.

Problem 1: provided the compound MgO, recognize its combined charge.

Steps come Solve:

1. Create out the dues of its ions: Mg+2 and also O-2

2. Multiply this charges: (2) x (-2) = -4

Problem 2: provided the link KCl, recognize its merged charge.

1. Compose out the dues of that is ions: K+1 and also Cl-1

2. Multiply this charges: (1) x (-1) = -1

We deserve to compare the -4 charge of MgO to the -1 fee of KCl as discussed. As the previous is 4 times the amount of the latter, we can predict the its lattice power would be approximately 4 times better as well.

Now, us will practice solving for the dimension variable.

Problem 3: given the compound CaO, recognize the size of its ions.

Steps come Solve:

1. Determine the ionic radii that its cation: Ca+2 has an ionic radius the 0.100 nm.

2. Identify the ionic radii of its anion: O-2 has actually an ionic radius the 0.140nm.

We can compare these worths to those of one more ionic compound together discussed. This gives insight right into which exhibits larger lattice energy.

Born-Haber Cycle Examples

Now, us will exercise solving for precise lattice power using the Born-Haber Cycle.

Problem 1: given the compound NaCl, determine its lattice energy.

Steps to Solve:Write the reaction describing the formation of NaCl under regular conditions:


Change the reactants right into their ionic gas components.




This final transformation shows the development of the “lattice” compound itself.

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3. In accordance v Hess’s law, different the components of the reaction and consider lock in isolation.