Gen Chem_Ch 6_18th_Electron Configuration (3)
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Overview
Dr. Reza Latifi explains how to write full and noble-gas shorthand electron configurations, identify valence electrons, and use orbital diagrams to determine whether an atom is paramagnetic. He applies these rules to oxygen ions and transition metals, including iron and nickel, emphasizing that transition-metal cations lose 4s electrons before 3d electrons.
Key takeaways
- Noble-gas shorthand compresses a configuration by replacing the filled core with the preceding noble gas, as sodium’s 1s2 2s2 2p6 3s1 becomes [Ne] 3s1.
- For a main-group element, valence electrons are counted from the outer-shell ns and np subshells; oxygen has six from 2s2 2p4.
- Neutral oxygen is paramagnetic because its 2p4 arrangement contains two unpaired electrons.
- Oxygen’s anion and cation configurations are formed by changing the 2p occupancy: O- is 2p5, while O+ is 2p3.
- Iron’s [Ar] 4s2 3d6 configuration has eight counted valence electrons when 4s and 3d electrons are included, placing it in group 8.
- For the nickel examples, ionization removes 4s electrons before 3d electrons: Ni+ is [Ar] 4s1 3d8 and Ni2+ is [Ar] 3d8.
Chapters
- Sodium’s full configuration, 1s2 2s2 2p6 3s1, becomes [Ne] 3s1 by replacing the neon core with the previous noble gas.
- Oxygen has the configuration 1s2 2s2 2p4; its second-shell valence count is 2s2 plus 2p4, for six electrons.
- Oxygen’s 2p4 orbital diagram has two unpaired electrons, making neutral oxygen paramagnetic.
- To form O-, add one electron to neutral oxygen’s 2p subshell, giving 1s2 2s2 2p5.
- To form O+, remove one electron from oxygen’s 2p subshell, giving 1s2 2s2 2p3.
- Boron’s 2s2 2p1 configuration illustrates that added electrons enter available 2p orbitals, while electrons are removed from the higher-energy 2p subshell before 2s.
- For main-group elements, the valence count comes from the outer-shell ns and np electrons.
- Iron has the shorthand configuration [Ar] 4s2 3d6; its highest principal quantum number is n = 4, so it is in period 4.
- Counting iron’s 4s2 and 3d6 electrons gives eight valence electrons, corresponding to group 8, also shown as 8B in some older group labels.
- When nickel loses electrons, the 4s electrons are removed before the 3d electrons: Ni+ is [Ar] 4s1 3d8 and Ni2+ is [Ar] 3d8.
- The lecture’s final worked rule is to remove electrons from the occupied orbital with the highest principal quantum number, which is 4s for these transition-metal examples.
Transcript excerpt
0:11 [music] >> Hello and welcome back and thank you very much for watching another lecture from Gerald chemistry. And last lecture I said electron configuration of for example sodium it can be written as 1s 1s2 2s2 2p6 3s1 and we said electrons of the last layer or the valence shell we call them valence electrons and we can write it that way we call it full electron configuration or we can say sodium sodium is equal to the previous noble gas you look at the sodium in the periodic table and find the previous noble gas which is neon and then now after that one you write the valence shell which is the 3s with one electron and what was the reason behind it? And the reason is this that when you look to electron configuration of neon is 1s2 2s2 2p6 so it's really equal to
1:00 this part technically they are sharing those orbitals and so what's the need of you know to rewrite them and why don't you save time and space by just simply saying neon 3s1 and then just move and move on and this is going to be technically the short electron configuration of sodium. Now when it comes to taking electron or adding electron to a main element and this this is going to be the policy that we will follow. For example let's say we have oxygen I go oxygen it has eight electrons and so I go 1s2 2s2 and then I go 2p 4 this element belong to the second period of the periodic table and the valence electrons you go ns ns plus np of that layer the valence shell okay which is this shell. So you say valence electrons equal to we have
1:49 two electrons inside s orbital plus four
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Related notes
Summary, takeaways, and chapters were generated by AI from the video's transcript and may contain errors. The video belongs to its creator, Dr. Reza Latifi at Oklahoma State University, OSU.