We are being asked to identify which compound has a higher magnitude lattice energy between NaCl and MgCl_{2}

$\overline{){\mathbf{Ionic}}{\mathbf{}}{\mathbf{Bond}}{\mathbf{}}{\mathbf{Energy}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}\frac{|\mathrm{cation}\mathrm{charge}\xb7\mathrm{anion}\mathrm{charge}|}{\mathbf{cationradius}\mathbf{}\mathbf{+}\mathbf{\hspace{0.17em}}\mathbf{anion}\mathbf{}\mathbf{radius}}}$

Radius = period number

• To determine the cation and anion charge, recall that some elements have common charges based on what **group** they belong to on the periodic table:

Group 1A +1 charge

Group 2A +2 charge

Group 3A +3 charge

Group 4A *typically do not gain or lose e ^{-} until Tin (Sn) and Lead (Pb)*

Group 5A -3 charge

Group 6A -2 charge

Group 7A -1 charge

• For their cation and anion radius, r*efer to the periodic table to determine which period the atom belongs to*

**Calculate the Lattice Energy (Ionic Bond Energy) of each compound given:**

**NaCl**

• Na

▪ Group 1A → +1 charge → Na^{+}

▪ Period = 3

• Cl

▪ Group 7A → -1 charge → Cl^{-}

▪ Period = 3

$\mathbf{Ionic}\mathbf{}\mathbf{Bond}\mathbf{}\mathbf{Energy}\mathbf{}\mathbf{=}\mathbf{}\frac{|\mathrm{cation}\mathrm{charge}\xb7\mathrm{anion}\mathrm{charge}|}{\mathbf{cationradius}\mathbf{}\mathbf{+}\mathbf{\hspace{0.17em}}\mathbf{a}\mathbf{nion}\mathbf{}\mathbf{radius}}\phantom{\rule{0ex}{0ex}}\mathbf{Ionic}\mathbf{}\mathbf{Bond}\mathbf{}\mathbf{Energy}\mathbf{}\mathbf{=}\mathbf{}\frac{|\left(+1\right)\xb7\left(-1\right)|}{\mathbf{3}\mathbf{}\mathbf{+}\mathbf{\hspace{0.17em}}\mathbf{3}}\phantom{\rule{0ex}{0ex}}\mathbf{Ionic}\mathbf{}\mathbf{Bond}\mathbf{}\mathbf{Energy}\mathbf{}\mathbf{=}\mathbf{}\frac{1}{\mathbf{6}}$

**Ionic Bond Energy = 0.17 **

Which compound has a higher magnitude lattice energy: NaCl or MgCl_{2}?

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