## Best Formal Charge

$FC=V-(L+\frac{S}{2})$

Tracy Tolentino_2E
Posts: 140
Joined: Sat Sep 07, 2019 12:17 am

### Best Formal Charge

How do we know if the structure is the best if the formal charge for all the atoms are not 0? Like is it better for the outer atoms to have a formal charge of 0 while the central atom is not 0 or would the opposite be better?

Maya Serota 3G
Posts: 53
Joined: Tue Sep 24, 2019 12:17 am

### Re: Best Formal Charge

You want the most electronegative atom to carry any extra negative charge and the least electronegative atom to carry any extra positive charge.

Kristina Rizo 2K
Posts: 105
Joined: Wed Sep 18, 2019 12:19 am

### Re: Best Formal Charge

Maya Serota 3G wrote:You want the most electronegative atom to carry any extra negative charge and the least electronegative atom to carry any extra positive charge.

So this means that any atom closer to the top right of the table should be the ones to carry the negative charge since they have a stronger pull on electrons right?

Manav Govil 1B
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

### Re: Best Formal Charge

For the question right above this comment:

Exactly. Atoms such as fluorine and oxygen are highly electronegative and are able to pull electrons closer to themselves. Putting a negative on them only makes sense because they have a natural tendency to be negative in a molecule.

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

### Re: Best Formal Charge

Manav Govil 4A wrote:For the question right above this comment:

Exactly. Atoms such as fluorine and oxygen are highly electronegative and are able to pull electrons closer to themselves. Putting a negative on them only makes sense because they have a natural tendency to be negative in a molecule.

This is correct. Additionally, it is important to note that it is very unlikely for an extremely electronegative element (such as O, N, F, Cl) to have a positive charge, as the ionization energy of those elements is extremely high. To summarize what others are saying, place the most negative formal charge on the most electronegative element in order to show that the most electronegative element will be the most likely to attract the bonding electron.

Ruby Richter 2L
Posts: 103
Joined: Thu Jul 25, 2019 12:17 am

### Re: Best Formal Charge

I'm a little confused about what ionization energy has to do with the fact that it is very unlikely for an extremely electronegative element (such as O, N, F, Cl) to have a positive charge?

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

### Re: Best Formal Charge

Ruby Richter 4G wrote:I'm a little confused about what ionization energy has to do with the fact that it is very unlikely for an extremely electronegative element (such as O, N, F, Cl) to have a positive charge?

Ionization energy is the energy needed to remove an electron. Elements that have high ionization energies have high ionization energies because the positive charge in the nucleus has a greater pull on the valence electrons (the effective nuclear charge is larger). If elements are very electronegative, they have a high affinity for bonding electrons, meaning that since they have a higher effective nuclear charge, the electrons are mole likely to be distributed closer to that element. To answer your question, if an element has a high electronegativity, it must have a high effective nuclear charge (or relative pull of the nucleus on valence electrons), meaning that it will take MORE energy to take one electron away from the element (Ionization energy). Since the effective nuclear charge is large for very electronegative elements, it is going to take a lot more energy to remove an electron (make the atom more positive). I hope that helps

Juana Abana 1G
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

### Re: Best Formal Charge

Yes, the most electronegative atom should be the one to carry the negative charge since it has a stronger pull of electrons.

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