# Li br li br 9 4 922 plan find the charge of the known

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Li + Br Li + Br + 9-4
9.22 Plan: Find the charge of the known atom and use that charge to find the ionic charge of element X. For A-group cations, ion charge = the group number; for anions, ion charge = the group number – 8. Once the ion charge of X is known, the group number can be determined. Solution: . 2A(2)
9.24 Plan: Find the charge of the known atom and use that charge to find the ionic charge of element X. For A-group cations, ion charge = the group number; for anions, ion charge = the group number – 8. Once the ion charge of X is known, the group number can be determined. Solution: a) X in X 2 O 3 is a cation with +3 charge. The oxygen in this compound has a –2 charge. To produce an electrically neutral compound, 2 cations with +3 charge bond with 3 anions with –2 charge: 2(+3) + 3(–2) = 0. Elements in Group 3A(13) form +3 ions. b) The carbonate ion, CO 3 2– , has a –2 charge, so X has a +2 charge. Group 2A(2) elements form +2 ions. c) X in Na 2 X has a –2 charge, balanced with the +2 overall charge from the two Na + ions. Group 6A(16) elements gain 2 electrons to form –2 ions with a noble gas configuration. 9.25 a) 7A(17) b) 6A(16) c) 3A(13) 9.26 Plan: The magnitude of the lattice energy depends on ionic size and ionic charge. For a particular arrangement of ions, the lattice energy increases as the charges on the ions increase and as their radii decrease. Solution: Solution:
a) BaS has the lower lattice energy because the ionic radius of Ba 2+ is larger than Ca 2+ . A larger ionic radius results in a greater distance between ions. The lattice energy decreases with increasing distance between ions. b) NaF has the lower lattice energy since the charge on each ion (+1, –1) is half the charge on the Mg 2+ and O 2– ions. Lattice energy increases with increasing ion charge.