QUESTION: Which atom’s first five ionization energies best resembles the pattern shown in the graph? A. Na, B. Mg, C. Al, D. K First ionization energy: X(g)  X+(g) + e- Second ionization energy: X+(g)  X2+(g) + e- Third ionization energy: X2+(g)  X3+(g) + e- Fourth ionization energy: X3+(g)  X4+(g) + e- Fifth ionization energy: X4+(g)  X5+(g) + e- SCRIPT: Which atom’s first five ionization energies best resembles the pattern shown in the graph? A. Na, B. Mg, C. Al, D. K PAUSE CLICK First ionization energy refers to the energy needed to remove an electron from an atom. HIGHLIGHT bar The second ionization energy of the atom refers to the energy needed to remove another electron after one has been removed. The third ionization energy of the atom refers to the energy needed to remove a third electron, after two electrons have been removed. CLICK The fourth ionization energy of the atom refers to the energy needed to remove a third electron, after three electrons have been removed. The fifth ionization energy of the atom refers to the energy needed to remove a third electron, after four electrons have been removed. Note that every time you remove an electron, it gets harder to remove the next one. Note that the first through fifth ionization energy leads to the formation of cations with charge of +1 CLICK +2 +3 +4 CLICK and +5 Respectively. The drastic increase from third to fourth ionization energy HIGHLIGHT 3rd and 4th bar Suggests that a noble-gas like configuration is achieved after the removal of the third electron. Once a noble gas like configuration is achieved, it becomes drastically more difficult to remove the next electron. So, let’s examine the electron configurations of the choices given… Sodium’s electron configuration is… neon core, 3s1 For magnesium, the electron configuration is… neon core, 3s2 For aluminum, the electron configuration is… neon core, 3s2, 3p1 And for potassium, the electron configuration is… argon core, 4s1 Of the choices given, aluminum is the only atom that has attains a noble-gas-like configuration upon removal of Three electrons. HIGHLIGHT 3s2 and 3p1 Removal of the electron from 3s and 3p subshell of aluminum leaves behind the neon core. Therefore, the correct answer is aluminum For sodium and potassium, we would expect a drastic increase in going from first ionization energy To second ionization energy because removal of the first electron leaves behind a noble gas core, from which it Would be much more difficult to remove a second electron. Similarly we would expect a drastic increase from second to third ionization energy for magnesium. END RECORDING

QUESTION: Which atom’s first five ionization energies best resembles the pattern shown in the graph? A. Na, B. Mg, C. Al, D. K The drastic increase from third to fourth ionization energy suggests that a noble-gas like configuration is achieved after the removal of the third electron. It is extremely difficult to remove an electron from a noble-gas like configuration. Na: [Ne] 3s1, Mg: [Ne] 3s2 Al: [Ne] 3s2 3p1, K: [Ar] 4s1

Video ID: 2-6-7 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08