The ionization energies of Li, Be⁺, B²⁺, and C³⁺ are, respectively, 520, 1757, 3659, and 6221 kJ mol^–1. The ionization energies Na, Mg⁺, Al²⁺, and Si³⁺ are (from Table 9.4) 495.8, 1451, 2745, and 4356 kJ mol^–1. Plot a graph of the square roots of the ionization energies versus the nuclear charge for these two series. Explain the observed relationship with the aid of Bohr’s expression for the binding energy of an electron in a one-electron atom.

Table 9.4

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TABLE 9.4 lonization Energies of the Third-Period Elements (in kJ mol-¹) Si P S Ar Na Mg Al 495.8 737.7 First 577.6 1,012 999.6 1,251.1 1,520.5 Second 4,562 1,451 1,817 1,903 2,251 2,297 2,666 Third 7,733 2,745 2,912 3,361 3,822 3,931 Fourth 4,957 4,564 5,158 5,771 6,274 7,013 6,542 7,238 21,270 8,496 9,362 8,781 27,110 11,020 12,000 Fifth Sixth Seventh 786.5 1,577 3,232 11,580 4,356 16,090 CI