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Central atom

Posted: Fri Nov 01, 2019 10:44 am
by Ying Yan 1F
When drawing lewis structures, how should I go about determining the central atom? I noticed on a lot of molecules that even though Oxygen has the higher ionization energy, Carbon or Sulfur is the central atom. Thanks!

Re: Central atom

Posted: Fri Nov 01, 2019 11:18 am
by AnvitaaAnandkumar_1B
The central atom is usually the one with the lowest electronegativity or the least numerous element.

Re: Central atom

Posted: Fri Nov 01, 2019 11:21 am
by Alexa Mugol 3I
In the lecture, I believe Dr. Lavelle put that the central atom is the one with the lowest ionization energy. A good rule of thumb is that carbon is almost always the central atom.

Re: Central atom

Posted: Fri Nov 01, 2019 11:21 am
by 005384106
When drawing lewis structures, you should look at the compound and notice where the atoms are placed on the electron negativity scale. The least electronegative atom is usually your central atom. However there are exceptions such as noble cases.
Also sometimes the least moles of the atom in the compound is your central atom.
Ex. CO2 C is the central atoms because it has the least amount of element (1) compared to Oxygens 2 atoms.
Hope this helped! :)

Re: Central atom

Posted: Fri Nov 01, 2019 11:28 am
by Sartaj Bal 1J
Along with following the trends of lowest electronegativity/ionization energy for the central atom, a lot of molecules also tend to display some sort of symmetry. For example, CH4 achieves symmetry with the central atom, C, being surrounded by the four hydrogen atoms. Also, Hydrogen can never be the central atom due to its ability to only form one covalent bond.

Re: Central atom

Posted: Fri Nov 01, 2019 12:39 pm
by Junxi Feng 3B
The central atom is always the one with the least electronegativity. Also, central atom will be the one that has the most unpaired valence electrons. In most of the cases, it should be fairly easy to find the central atom, such as CO2, BF4, SO4., etc., apparently you cannot put oxygen or fluorine in the center in these cases.

Re: Central atom

Posted: Fri Nov 01, 2019 12:40 pm
by Eunice Nguyen 4I
Professor Lavelle said that the central atom will have the lowest ionization energy.