Choice B: Br2(l)  Br2(g)  2 Br(g)  2 Br+(g) + 2e- QUESTION: The ionization energy of bromine atoms is the energy associated with which of the following? A. Br(g)  Br+(g) + e- B. Br2(l)  2 Br+(g) + 2e- C. Br(g) + e-  Br-(g) D. Br2(l) + 2e-  2 Br-(aq) Ionization energy = energy needed to remove an electron from an isolated atom. Choice B: Br2(l)  Br2(g)  2 Br(g)  2 Br+(g) + 2e- NOTE: energy associated with C is called the “electron affinity of bromine” SCRIPT: The ionization energy of bromine is the energy associated with which of the following? A. atomic bromine in the gas phase … yields Br+ ion in the gas phase …plus electron B. Diatomic bromine molecule in the liquid phase… yields two Br+ ions in the gas phase… plus 2 electrons C. Atomic bromine in the gas phase… plus electron… yields bromide ions in the gas phase Or D. Diatomic bromine molecules in the liquid phase…. Plus two electrons… yields two bromide ions in aqueous solution PAUSE CLICK The ionization energy of an atom is defined as the energy needed to remove an electron from an isolated atom. HIGHLIGHT remove an electron Choices C and D do not involve removal of electron. They involve gaining of electrons. So we can eliminate these choices. CLICK Choice B can also be eliminated because the bromine atoms in Br2 are not isolated. By isolated atoms, we mean atoms not bonded to any other atom, and nowhere near any other atom, which is the case in the gas phase. Choice B involves much than just ionization of bromine atoms. It involves vaporization of diatomic bromine molecules HIGHLIGHT Br2(l)Br2(g) followed by the dissociation of the diatomic molecules in the gas phase to individual bromine atoms HIGHLIGHT Br(2)  2 Br(g) Then by the ionization of the bromine atoms HIGHLIGHT 2 Br(g)  2 Br+(g) + 2e- Therefore… the correct answer is A. By the way, Choice C is the opposite of choice A. The energy associated with this process is called the electron affinity of bromine. HIGHLIGHT electron affinity and choice C. The electron affinity of an atom is the energy associated with the gaining of one electron by an atom. END RECORDING

Video ID: 2-6-3 © 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