1. To construct the ground state electron configuration,
QUESTION:
Which of the following is the ground state electron configuration of Al? A. [Ne] 3s2 3p1 B. [He] 2s2 2p6 3s2 3p1
C. [Mg] 3p1
D. all of the above
To construct the ground state electron configuration,
We first determine number of electrons
We assign electrons to subshells following the Aufbau principle. Fill lowest energy subshells first.
The CORE configuration may be abbreviated using noble gas symbol enclosed in square brackets..
SCRIPT:
Which of the following is the ground state electron configuration of a sulfur atom? Neon core… 3s2….3p1
Helium core…. 2s2 2p6 3s2 3p1
Magsesium core… 3p1 Or
All of the above
PAUSE CLICK
TO construct the ground state electron configuration of an atom, we do the following
CLICK
First, we determine the number of electrons
CLICK Then we assign electrons to subshells following the Aufbau principle. We fill the lowest energy subshells first.
CLICK The core configuration may be abbreviated using the symbol for a noble gas enclosed in square brackets.
Of the choices given above, C and D are obviously wrong because magnesium….
HIGHLIGHT Mg
is not a noble gas….
Helium and Neon are both noble gases, so which symbol should we use?
We use the symbol for the noble gas that immediately precedes the element.
In this case, it’s neon.
The correct answer is A.
But how do we come up with the answer, if this were not a multiple choice question.
Let’s refer to the periodic table.
Here’s aluminum….
It’s in the third row or third period…..
The noble gas immediately preceding aluminum is the noble gas in the second row….neon….
We can see that aluminum has an atomic number of thirteen. An aluminum atom has 13 electrons.
And that neon has an atomic number of 10. A neon atom has 10 electrons.
Let’s assign the electrons.
The first subshell is the 1s subshell.
We can put a maximum of two electrons in an s subshell.
The next subshell is the 2s subshell.
CLICK The next two electrons are assigned to the 2s subshell.
CLICK The next subshell is the 2p subshell
CLICK Since a p subshell can accommodate a maximum of six electrons, we assign the next six electrons to the 2p subshell
At this point, we have assigned ten electrons… equals We now have the electron configuration for Neon.
1s2 2s2 2p6
The next subshell is the 3s subshell
CLICK We assign the next two electrons to this subshell.
So far… we have assigned 12 electrons… We have one more to assign to get the electron configuration of aluminum.
CLICK The thirteenth electron goes into the the next subshell ---- the 3p subshell…
CLICK Therefore, the ground state electron configuration of an aluminum atom is…
1s2 2s2 2p6 3s2 3p1
Or…
we can replace 1s2 2s2 2p6 by the neon core symbol.
PAUSE 2 seconds
END RECORDING

2. 1s 2s 2p 3s
Al: 13 electrons
Ne: 10 electrons
1s2
2s2
2p6
3s2
3p1
[Ne]

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