1. Na: 11 electrons, Na+: 10 electrons
QUESTION:
All of the following have the same electron configuration except…? A. Ne B. Na+, C. O-, D. O2-
SCRIPT:
All of the following have the same electron configuration except…? A neon atom…
A sodium ion with a charge of +1
An F minus ion
Or An O minus ion
PAUSE
CLICK
Let’s locate these elements in the periodic table.
Here’s neon,
a neon atom has 10 electrons.
CLICK Here’s sodium
CLICK A sodium atom has 11 electrons….one more than Neon.
But the question is asking for a sodium ion with a +1 charge…. Sodium ion with a plus one charge has 10 electrons. The same number as neon.
Here’s oxygen.
An oxygen atom has 8 electrons… two less than neon
CLICK But the question is asking for a O minus, and O two minus ions ….
A negative charge means one additional electron… So O minus has 9 electrons, one less than neon.
And O, 2 minus, has two 10 electrons, the same number as Neon.
We can see that choices A, B and D all have the same number of electrons --- ten ---- we expect them to have the same electron configuration.
The answer is choice C. O minus is the only one that is not isoelectronic with the others.
When main group atoms like sodium and oxygen form ions, they tend to do so in a manner that leads to a noble-gas-like configuration.
We say that the ions we’re likely to find in nature are isoelectronic with a noble gas.
In the cases given here, sodium and oxide ions with neon
CALLOUT “Isolectronic” pointing to Ne, Na+, and O2-
We do not expect to find O-
CLICK Here are the electron configurations.
For neon, which has ten electrons, it’s 1s2 2s2 2p6
HIGHLIGHT configuration
For sodium, which has eleven electrons, it’s 1s2 2s2 2p6 3s1
Sodium ion tends to lose its outermost electron HIGHLIGHT 3s1
To form sodium ion. So, for sodium ion, the electron configuration is 1s2 2s2 2p6, …
just like neon. Sodium ion is isoelectronic with neon
For oxygen, which has 8 electrons, the electron configuration is 1s2 2s2 2p4….
For O minus, we add one more electron to the 2p subshell
HIGHLIGHT 2p5
Another electron added and we get the oxide ion, which is also isoeelctronic with neon.
PAUSE END RECORDING
Ne: 10 electrons
Na: 11 electrons, Na+: 10 electrons
O: 8 electrons, O-: 9 electrons, O2-: 10 electrons

2. QUESTION:
All of the following have the same electron configuration except…? A. Ne B. Na+, C. F-, D. O-
Ne: 1s2 2s2 2p6
Na: 1s2 2s2 2p6 3s1  Na+: 1s2 2s2 2p6
O: 1s2 2s2 2p4  O-: 1s2 2s2 2p5  O2-: 1s2 2s2 2p6
Na+ and O2- are isoelectronic with 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