Chapter 9, Problem 117DIA

The first graph shown here is of the first ionization energies (the energy associated with removing an electron) of the period 3 elements. The second graph shows the electron affinities (the energy associated with gaining an electron) of the period 3 elements. Refer to the graphs to answer the question.

(a) Notice that ionization energies are positive and the electron affinities are negative. Explain the significance of this difference. (b) Describe the general trend in period 3 first ionization energies as you move from left to right across the periodic table. Explain why this trend occurs. (Hint: Consider the trend in atomic size as you move from left to right across the periodic table.)

(c) The trend in first ionization energy has two exceptions: one at Al and another at S. Write the electron configurations of Mg, Al, P, and S and refer to them to explain the exceptions.

(d) Describe the general trend in period 3 electron affinities as you move from left to right across the periodic table. Explain why this trend occurs. (Hint: Consider the trend in atomic size as you move from left to right across the periodic table.)

(e) The trend in electron affinities has exceptions. Write the electron configurations of si and explain why the electron affinity for Si is more exothermic than that of P.(f)Determine the overall energy change for removing one electron from Na and adding that electron to Cl. Is the exchange of the electron exothermic or endothermic?

First Ionization Energies of Period 3 Elements

Electron Affinities of Period 3 Elements