1. Ionization energy of Mg2+ >> Mg
QUESTION:
Which of the following has the highest ionization energy? A. Ne B. Mg2+, C. Mg, D. F-
Ionization energy of Mg2+ >> Mg
SCRIPT:
Which of the following has the highest ionization energy?
Neon… magnesium ion … magnesium…. Or fluoride ion
PAUSE
One choice should immediately stand out as an incorrect answer.
It’s always harder to remove an electron from a positive ion compared to the original atom.
Magnesium, choice C, has a lower ionization energy than magnesium ion.
CROSS OUT choice C
You need to take out two electrons from a magnesium atom to get a magnesium ion.
It’s much harder to take out a third electron after that.
CLICK

2. Mg: [Ne] 3s2  Mg2+: [Ne] F: [He] 2s2 2p5  F-: [Ne] SCRIPT, slide 2
Here’s neon
CLICK here’s magnesium,….
CLICK
Magnesium has two more electrons than neon… so its electron configuration is
CLICK neon core… 3s2
Since magnesium ion has a charge of +2, it is isoelectronic with neon.
HIGHLIGHT [Ne] (next to Mg2+)
And here’s fluroine.
It has one electron less than neon.
Therefore, fluoride ion, which has a charge of negative one, is also isoelectronic with Neon.
CLICK CONTINUED ON NEXT SLIDE
Mg: [Ne] 3s2  Mg2+: [Ne]
F: [He] 2s2 2p5  F-: [Ne]

3. Ne, Mg2+, and F- are isoelectronic: 1s2 2s2 2p6
QUESTION:
Which of the following has the highest ionization energy? A. Ne B. Mg2+, C. Mg, D. F-
Ne, Mg2+, and F- are isoelectronic: 1s2 2s2 2p6
Nuclear charge: Ne: +10 Mg: +12 F: +9
1s2
SCRIPT:
Since Neon, magnesium ion, and fluoride ion are isoelectronic…. They all have a configuration of 1s2 2s2 2p6.
That means two electrons in the core
HIGHLIGHT 1s2
And eight electrons in the valence shell.
HIGHLIGHT 2s2 2p6
So, how do we determine which of the three has the highest ionization energy.
Let’s try to visualize the factors involved.
Here’s the nucleus.
CLICK Here’s the core…. with two electrons.
CLICK and here’s the valence shell, with eight electrons
CLICK
The ionization energy depends on how strongly the valence electrons are held by the atom.
There are two factors that determine this.
CLICK One is the inward pull due to the nucleus. The nucleus, which is positive, exerts an inward pull on the valence electrons.
CLICK The second factor is the repulsions among the electrons. The core electrons will exert an outward push on the valence electrons.
CLICK The the valence electrons also exert an outward push on one another
Since the electron configurations are all the same. The second factor doesn’t matter.
What matters, then is how many protons in the nucleus are pulling in the valence electrons.
The number of protons is just the atomic number. We can get this information from the periodic table
Neon has 10 protons, so its nuclear charge is +10
HIGHLIGHT
Magnesium has 12 protons; its nuclear charge is +12
HIGHLIGHT and fluorine has 9 protons; its nuclear charge is +9.
Therefore, the electrons of magnesium will experience the strongest pull from the nucleus. They will be more difficult to remove than the valence electrons in neon or fluoride.
The correct answer is B.
PAUSE CLICK END RECORDING

4. 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