Central atom

[Sarah Brecher 1I]

On homework question 3.33 part b, they asked for the lewis structure of COCl2. Which atom goes in the middle and how do you know this?

[Jack Martinyan 1L]

Carbon would go in the middle because it has the lowest ionization energy

[Caroline Crotty 1D]

When drawing Lewis structures, the lowest ionization energy will always go in the middle because it requires the least amount of energy to share the electrons.

[Corryn Doll]

The central atom will always be the one with the lowest ionization energy. To find this, you can look on the periodic table at were each atom lies. The ionization energy increases across a period and decreases down a group. Thus you want to look for the atom that is furthest to the left and closest to the top.

In your case, between C, O, and Cl, Carbon lies above Cl but on the same level as O. However, C is further left than O and thus has the lowest ionization energy of those atoms involved. If you remeber this trend, the periodic table will tell you the rest of what you need to know as far as the central atom and ionization energy.

Hope this helped!! :)

[Joanna Pham - 2D]

Wait, where are you guys getting ionization energy from? I thought the central atom has to be the element that was the least electronegative, which is why C is the central atom since it has the electronegativity

[Tina Wen 1G]

Usually the atom with the fewest valence electrons is the central atom. It has more space accept electrons shared with other atoms. Hence carbon goes in the middle since it has 4 valence electrons and can form 4 bonds with surrounding atoms.

[Valeria Viera 1B]

I agree with Joanna,
The central atom should I always be the one with the least electronegativity
The trend in periodic table increases going up and to the right
Out of Cl, O, and C in this example C is the most left so it has the least electronegativity

[princessturner1G]

Wait, where are you guys getting ionization energy from? I thought the central atom has to be the element that was the least electronegative, which is why C is the central atom since it has the electronegativity

Ionization energy follows the same trend as electronegativity, so you can think of it as either the lowest ionization energy or the least electronegative for the central atom.