Mass of proton or neutron: 1.0 u Mass of electron: u

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Ionization energy of Mg2+ >> Mg

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Presentation transcript:

Mass of proton or neutron: 1.0 u Mass of electron: 0.0005 u QUESTION: Which of the following is false? A. An atom’s mass is concentrated in the nucleus B. The atom’s nucleus is positively charged C. The number of electrons in an atom is equal to the number of protons D. The number of protons in an atom is equal to the number of neutrons Mass of proton or neutron: 1.0 u Mass of electron: 0.0005 u Protons and neutrons are found in the nucleus. Neutrons are electrically neutral (charge=0) Proton is positively charged (“+1” or 1.6x10-19 C) Electron is negatively charged ( “-1” or -1.6x10-19 C) Atom is neutral: # protons EQUALS # electrons SCRIPT: Which of the following is false? A. An atom’s mass is concentrated in the nucleus B. The atom’s nucleus is positively charged C. The number of electrons in an atom is equal to the number of protons D. The number of protons in an atom is equal to the number of neutrons PAUSE CLICK. The mass of a proton or neutron is approximately 1 atomic mass unit. On the other hand, the mass of an electron is about 2000 times less. Since protons and neutrons are found in the nucleus, choice A is true. The bulk of an atom’s mass is due to protons and neutrons and they are found in the nucleus. CALLOUT “TRUE” next to choice A CLICK Neutrons are electrically neutral. We say that they have zero charge. But a proton is positively charged. It’s actual charge is 1.6x10-19 coulombs. In atomic units, this is given a value of +1. Since the protons are found in the nucleus, choice B is true. The nucleus must be positively charged. An electron is negatively charged. Its charge is equal in magnitude to that of a proton. So, we say that the charge of an electron is –1.6x10-19 coulombs, or –1 atomic units. Since an atom is electrically neutral, the number of protons must equal to the number of electrons. Therefore, choice C is also true. CLICK The false statement, then, … is choice D. The number of protons need not be equal to the number of protons. The correct answer is choice D. PAUSE CLICK END RECORDING

Video ID: 1-10-3 © 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