How To Find The Lattice Energy Of A Compound

Lattice energy is the a measure of how strong an ionic bond is. An ionic bond is the joining together of two electrically charged atoms called ions in order to form a compound. A common example of a compound formed from an ionic bond is table salt, sodium chlorine NaCl. The Born-Lande equation is used to find the lattice energy of a compound, and the formula for the equation is E = [-(NA)(M)(Z+)(Z-)/4(pi)(e0)(r0)][1-(1/n)]. While this may look exceedingly complicated, most of the equation is constants, meaning the values are the same every time.

Step 1

Plug in the constants. The constants in the equation are NA which is the symbol for Avogadro's constant 6.02214179(30)×10^23 mol; e, the elementary charge 1.602176487(40)×10^-19 c), and e0, the permittivity of free space, 8.854×10^−12 c^2 J^−1 mol^−1.

Step 2

Fill in the variables that change depending on the compound. The information that needs to be given is the Madelung constant represented as M, which, despite being called a "constant," as it is indeed constant within the compound itself, is different for each compound; the charge of the positive ion also called a cation, represented as Z+; the charge of the negative ion also called an anion, and shown as Z-; the distance to the nearest ion, shown as r0, and the Born exponent, represented as n, which is a number between 5 and 12.

Step 3

Solve the equation. The final value of lattice energy should be in kilojoules per mole.