1. QUESTION:
What is the electron configuration of naturally occurring aluminum ion? A. [Ne] 3s2 3p1, B. [Ne] 3s2
C. [Ne] 3s1, D. [Ne]
The electron configuration of an aluminum atom is 1s2 2s2 2p6 3s2 3p1, or [Ne] 3s2 3p1
Therefore: A is the electron configuration for Al B is the electron configuration for Al+ C is the electron configuration for Al2+ D is the electron configuration for Al3+
Al3+ is isoelectronic with Ne. Removal of 3 electrons makes it noble-gas-like. It is extremely hard to remove an electron from a noble-gas-like configuration. For main group metals (the “A” groups), naturally-occurring ions tend to be noble-gas-like (exceptions: post-transition metals like Pb)
SCRIPT:
What is the electron configuration of naturally occurring aluminum ion? A. [Ne] 3s2 3p1, B. [Ne] 3s2
C. [Ne] 3s1, D. [Ne]
PAUSE
CLICK
The electron configuration of an aluminum atom is 1s2 2s2 2p6 3s2 3p1, or neon core 3s2 3p1.
Therefore choice A is not the answer. Choice A is the electron configuration for an aluminum atom.
If we imagine removing the electron from the 3p subshell of choice A, then we get the electron configuration in choice B. Therefore, choice B is the electron configuration for an aluminum ion with a charge of +1. Similarly, choice C is the electron configuration for an aluminum ion with a charge of +2. And choice D is the electron configuration of an aluminum ion is +3.
SO which ion is the naturally-occurring ion. It turns out that the only ion of aluminum you’ll find in nature has a charge of +3. The answer is D. Why? CLICK Al3+ is isoelectronic with neon, which a noble gas. In other words, removal of three electrons from an aluminum atom takes out all the valence electrons, leaving behind a noble-gas-like configuration. It is extremely hard to remove an electron from a noble-gas-like configuration. This is generally observed among the main group metals, except for post-transition metals like lead. To make a post-transition metal noble-gas-like would involve the removal of not just the valence electrons, but ten electrons in an inner d subshell.
Here’s a periodic table with the main group metals highlighted in red and green. The post-transition metals are highlighted in green.
END RECORDING

3. Video ID: © 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