2.11 (1)

2.11 (1) - appear later on in the periodic table The 4s...

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Key for Micro Exam 2 Question 11 11. Which element or ion has the electron configuration of [Ar] 3d 6 ? (a) Cr (b) Fe (c) Cr 2- (d) Fe 2+ (e) Ca 2+ (f) Doesn’t exist Electron configurations are a method for accounting for all the electrons in an atom or ion. The element within brackets, [Ar], is always a noble gas that summarizes the electron configuration up to that point. In other words, the atom or ion in question has an identical electron configuration to [Ar] up to that point. Now, after [Ar] is written 3d 6 . What happened to the 4s electrons? Well, the 4s electrons are actually the first to be lost even though the 3d electrons
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Unformatted text preview: appear later on in the periodic table. The 4s electrons are exterior to the 3d and will be removed before those of the 3d orbital. So all we need to do is count six elements into the 3d level in order to know which atom we are dealing with. Count from Sc to the right and you’ll find that Fe is the sixth element in the group of 3d atoms. Since both of its 4s electrons have been removed, the Fe ion must have a +2 charge. 3d 4s...
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This document was uploaded on 11/04/2011 for the course CHEM 106 at BYU.

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